I just completed the game including all achievements for 100%. This guide will cover some gameplay basics, tips, achievements and other stuff I wish I'd known at the start of the game. The General Basics & Tips won't contain any real spoilers. The rest of the guide may contain spoilers about the main story, but I will give a warning if that's the case.

*(based on game version / latest update 27-09-2023)

Skills
At the start of the game you get the option to do an interview that will influence your starting skills. If you skip the interview you'll get a balanced character with 1 out of 3 stars in most skills, which is fine. During the game your skill levels will slowly improve and you can also hire navigators to gain additional skills.

If you take the interview you'll get 9 questions, each with 2 answers that boost a different skill. Personally I'd advise to prioritize Navigation, Leadership, Artillery, Swordplay and Logistics, in that order. Navigation improves sailing speed. Leadership decreases morale decline and is useful in many random events. Artillery increases sea battle damage. Swordplay does the same for land battle damage but is less important. And Logistics seems nice, but I found that shorter preparation periods aren't very useful. Medicine, History, Theology and Science are all equally unimportant.

Below are the skill boosters for each question with my personal recommendation in bold:
1. Swordplay / Artillery
2. Leadership / Logistics
3. Navigation / Artillery
4. Leadership / Medicine
5. Logistics / Medicine
6. Theology / Science
7. History / Theology
8. Swordplay / History
9. Navigation / Science

Sailing, speed and wind direction
The main part of this game consists of sailing around the world. Getting from city A to city B as fast as possible is important, since each day on the ocean you lose morale and supplies. This becomes especially important later in the game when you have to cover greater distances.

Your speed is shown with a number of colored arrows below your ship. Red is slow, orange is medium and blue is fast. If your sails align with the wind direction you'll move fast, no matter in which direction your ship is moving. The only exception is if you move in the exact opposite direction of the wind. In that case you can either point your sails in a 90 degrees corner to move with medium speed, or move your ship in a zigzag pattern to move fast. You also move faster in shallow (light blue) waters so try to sail close to the coast if possible

Finally, the wind direction in any given part of the world is always the same. For example, around Lisbon the wind always blows east and once you enter the Mediterranean Sea the wind will always turn west. Use this knowledge to find the most efficient route.

Ships
You can purchase bigger ships at the shipyard in Lisbon (and at some other cities) but they are very expensive, especially in the early game. A bigger ship is generally faster, but also carries more rooms that potentially slow it down. Therefore you shouldn't add any upgrades to your ship unless you really need them. In the first part of the game one canon and one cabin (for an additional navigator) are usually enough, and if you occasionally need more firepower you can remove the extra canons afterwards.

It's recommended to purchase a Caravel as soon as you have the chance. Note that the sell price is 80.000 gold but you'll pay only 53.000 since the value of your current ship will be deducted. Other useful upgrades are the Chart Room (for additional speed) and the Cargo Space (for extra gold). The Common Room is pretty useless since crew takes up very little space and this barely affects food and water consumption.

Movement on land:
Your default vehicle is a donkey, which is slow almost everywhere but relatively fast in the mountains. In several markets you can purchase a horse or a camel for 8000 gold. Horses move fast on plain terrain and forests, camels move fast in deserts and mountains. Later in the game you can find two more 'special' horses. You can switch between animals while riding by pressing F. Movement on land becomes more important later in the game.

Making money fast
Finishing contracts for the guild will earn you gold, but this isn't the most efficient way to make money. At every harbor you have an option to trade, and trade goods can usually be sold with a profit at harbors in a different country or region. Make sure to trade goods at every harbor whenever you can make a profit. Higher prices mean higher profits.

To increase profits from trading you can purchase and install the Cargo Space upgrade on your ship. An easy and profitable trade route at the start of the game is Lisbon – Casablanca. The most profitable trade route (by far!) in the current game version is Alexandria – Athens. If this is ever fixed in a future update, Athens – Istanbul is also very profitable.

Use one of these trade routes if you're ever in need of gold. Just don't overdo it at the start of the game. Later you will get a new skill (and probably a bigger ship) that makes it a lot easier to make gold through trading.

Time and contracts
Most activities like traveling, entering/leaving town or upgrading your ship consume time. This might give you the feeling that you're in a hurry, but you should never worry about time. No event is ever based on a specific date and you can never spend too much time on exploring or completing expeditions. The only aspect where time plays a role is with contracts, but you have more than enough time to complete them and you can always cancel and retry them without any real penalty.

You can only accept one contract at a time. Of course you are free to complete expeditions without accepting the contract first, but this is difficult since you can't get any hints. Traveling back and forth to Lisbon becomes annoying after a while. Luckily a feature is introduced later in the game that lets you accept and complete expeditions at any guild.

Battle
Fighting in the game is pretty straightforward if you ever played a game of rock, paper, scissors. You start with a deck of 5x rock, 5x paper and 5x scissors, and as the game progresses you can find improved cards. Note that you'll have to add them to your deck manually (Menu > Battle Deck) in order to use them in battle. 'Mighty' cards are an improved version of the original cards and deal 1,5x damage. A brown/yellow card like Rock Destroyer deals double damage, but loses to both paper and scissors, so it's best to use them only if you can see the enemy card.

Intuition improves the chances to see the enemy's cards. You should regularly drink at the tavern to boost this by 10%. You can check the icon in the upper left corner next to the date to see if the effect is still active.

Use intuition in combination with probability calculation to win battles. If your opponent has 5 cards and you can see only 2 of them, that doesn't mean the other cards are completely random. Let's say you can see 2 rocks and 3 question marks, the chances that those question marks are also rocks is considerably smaller, so it's best to counter them with scissors.

Sea fights:
Your damage is determined by your Artillery skill, the amount of canons and the equipped canon type. The Culverin (22 damage) is the strongest canon in the game. You can also improve the hull of your ship to increase its durability, but since this also affects your sailing speed I would only do this for the most difficult battles. Your ship should be fine most of the time without any armor.

Land fights:
Your damage is determined by your Swordplay skill and your equipped sword. The Claymore (24 damage) is the strongest sword throughout most of the game. The Plate Mail (17 defense) is the strongest armor in the game. With both these items equipped you shouldn't have any trouble in most physical battles.

Death / Defeat / Passing out
Losing in battle (sea or land) will result in death. In that case you will get a 'game over' and you are forced to return to your last save point. There are no other penalties for dying.

You can also pass out due to fatigue. This happens when you run out of morale/supplies on land or out of crew members at sea. Note that you can actually keep sailing for a pretty long time even after your morale and supplies have dropped to 0, as long as part of your crew is still alive. In contrast to death, passing out does not result in a 'game over'. You wake up in the most recent city and lose a fixed percentage of your gold as a penalty. This means that even if you pass out after a successful expedition, you can still complete that expedition at the guild.

Useful items
Here's a list of the best items in each category that you can find at the market. The items may be available in more places than the one listed below. Special items that are obtained through expeditions are not included.

Weapon: Claymore (damage 24), found in London for 15.000 gold
Armor: Plate Mail (defense 17), found in Genoa for 20.000 gold
Bag: Venetian Merchant's Bag (capacity 16), found in Venice for 50.000 gold
Canon: Culverin (damage 22), found in Copenhagen for ??? gold
Hull: Improved Steel Hull (durability +7), found in London for ??? gold
Figurehead: King Figurehead (battle spoils +15%), found in Lisbon for ??? gold

Your main focus in the early game should be to get the Claymore, Plate Mail and Culverin. The Venetian Bag is especially important for the late game expeditions and the Steel Hull can be useful in a few tough battles, but is no priority. The King Figurehead is the only figurehead you can find at a market and should only be bought if you have the spare coin for it. You can find more figureheads later in the game through expeditions.

(This part may contain spoilers! Read at your own risk if the words 'pirate hideout' or 'Dublin' don't ring any bells.)

Second Archibald fight
Let's skip ahead a bit, since the first part of the game is pretty straightforward. You're looking for Lucia's dad, found the eastern sea route to India and had some pirate trouble. After you beat Tyler and Amelia you're going after the big fish Archibald. You find out that he has a hideout north of Dublin. Right before you attack, the game will give you a warning that some major changes are about to happen, so this is a good moment to create a backup save file.

If you haven't already, make sure you upgrade your ship to a Caravel and get the Claymore (weapon), Plate Mail (armor), Culverin (canon) and Cargo Space (blueprint). Check the sections above for their locations and the fastest way to make money.

The second Archibald fight shouldn't pose too many problems if you prepared well. However, big changes are about to happen that will severely limit your movement range for some time. Also, in the upcoming event you will lose all the gold that you still have, so make sure you spend your remaining gold on items and ship upgrades, since you will get to keep those! After the Archibald fight, sail back to Lisbon to continue the story.

'Murica!
(This part contains spoilers if you haven't been to the western continent yet!)

…And then you're suddenly stuck in the Caribbean with a broken ship and a debt of 200.000 gold to a native chief. Collecting that much gold can be tedious work, so here's the quickest way to do it. If you were smart you already bought a bigger ship and the Cargo Space upgrade. Keep two canons on your ship to fight against Spanish attackers, add the Chart Room (if you have it), two Storage Rooms and fill the rest off your ship with Cargo Spaces. If you still have a small ship then 1 canon and 1 storage room should also suffice. Then sail back and forth between Havana and Veracruz to trade goods and use your newly acquired Haggle skill to greatly increase the profits. Especially the silver from Veracruz will sell for a nice price in the Spanish cities.

In the meantime, keep an eye out for items to repair your ship at each market. Once you obtained the required items and gold go back to the native chief. For your next mission you'll want to turn your trade vessel into a warship, so replace your Cargo Spaces with canons and start attacking those Spanish bastards!

Once you return to Lisbon you'll get your freedom of movement back. You can go wherever you want and it's up to you to decide if you want to focus on the main story or on random expeditions. The main story is again pretty straightforward from here. Just follow the instructions in the top-right corner of your screen.

Galleon
Since you already have at least 200.000 gold and the Haggle skill, the first thing you should do is save up money for a Galleon. This is the biggest ship in the game, with the highest default speed, the best durability and the most rooms. Arrange the ship at your own preference, but I found that the following lay-out worked really well throughout the whole game:

1 Chart Room
2 Canons
6 Storage Rooms
3 Cargo Spaces
1-3 Cabins (depending on your focus on expeditions)
1 Kitchen (an upgrade you get later in the game)

Remember that most ship upgrades negatively affect your sailing speed, so it's often better to leave a few rooms empty. You should also remove your Cargo Spaces once you've earned enough gold.

Other things to look out for
Apart from the main story you can now try to complete every expedition in the world (there's a total of 196). Don't forget to check the Royal library in Lisbon, since it also has some quests that aren't pert of the main story. Some expeditions will reward you with treasures or items that boost your default stats, like intuition or EXP gain. You can check your inventory to see their effects.

Below are a few items that are especially important to get:

• Red fiery horse: obtained after an expedition in China. This horse greatly increases your movement speed and range on land. It's at least twice as fast on any terrain except in the desert. Mainly useful for completing expeditions in Africa, India and South America where traveling on foot is often more efficient than traveling by ship.
  
• Spear of Longinus: obtained after an expedition in the Middle East. This is potentially the strongest weapon in the game. Its power is based on the amount of navigators you have and with 3 navigators it's about twice as strong as the Claymore.
  
• A super cute animal: obtained after an expedition in India (if I remember correctly). It reduces morale decline and is useful for expeditions where you need to travel in areas without places to rest.
  
• Demon Figurehead: obtained after an expedition in South America. Its effects are unknown but you will need it to complete the most difficult achievement in the game. Read the Achievements section below for more info.

Great explorer (found all finds)
In other words, finish all 196 expeditions in the game. In order to do that you first need to find every guild in the world and get the information about every expedition in their library. A few guilds that are easy to overlook are the ones in middle/northern China, India and the Middle East. (There are no guilds in South America, Australia or Middle/Southern Africa). Getting this achievement automatically means you finished at least 22 out of 24 available achievements. There are only 2 achievements that you can possibly miss. And then there's the Ghost Ship achievement/expedition that's a bit more complicated.

Navigator... Assemble! (hired 3 navigators)
Not the most difficult achievement, but it's possible to get the 'Great explorer' without getting this one. The only thing you need to do is get a ship with three cabins and hire three navigators (your main companions don't count) at the same time.

Celebrity (was awarded the title of Duke)
To get this achievement you need to upgrade yourself to the highest title at the court in Lisbon. You will need a lot of renown though. I think you need to complete around 150 expeditions before you have enough renown to get it.

Ghost ship (discovered the Ghost ship)
This is without a doubt the most difficult expedition, and you won't find it in any library. In order to get it you first need to complete a certain expedition to a waterfall in South America. Afterwards you will get the Demon Figurehead. Install it on your ship and the Ghost Ship contract will become visible in your expedition list. However, when you try to accept the contract at a guild, the guy doesn't want to talk about it and tell you to come back “when the dead and the living meet”.

Hint 1
'When dead and living meet' refers to Halloween (October 31) or Día de Muertos (November 2). Return to the guild on any of these days and the guy says you will probably find the Ghost Ship in a place that is furthest from land.

Hint 2
There is a spot in the ocean between South America and New Zealand called 'Point Nemo' that marks the furthest location on earth to the nearest coastline (thank you Google!). Sail to the coordinates 48 South, 123 West and circle around until you get a sudden feeling of death...

This battle is very difficult, so make sure you fully charged your ship and falcon special attacks, equip your best armor and weapons, drink at the tavern and add some canons for extra firepower. During the first stage you need to close the gap and deal enough damage to be able to enter the enemy ship. Then finish the job with your sword. Even with the perfect setup it may take several tries to win.