First things first – read the manual. “View the manual” is a prominent option when you launch the game for a good reason – you’ll be more than a bit lost without at least browsing through. Also, it contains delicious bread recipes :)

Next – go here:
https://terra-arcanum.com/drog/uap.html
http://www.terra-arcanum.com/downloads/

And download the unofficial patch (maybe the HD patch and level cap remover as well). The game is still buggy enough to need it.

Focus your starting character a bit (OF COURSE you’re going to create your own character. The starting characters are kinda garbage). Don’t try to be both a charismatic melee thief (Keys stats: Dex, Str, Melee, Dodge, Prowling, Lockpick, Perusasion, Chr) and a technologically inclined gunslinger inventor (key stats: A bunch :P) at the same time. Good first playthrough archetypes – the aforementioned Melee/Charisma thief, a Mage with Harm and Conveyance spells (most mages will want to branch out into Conveyance eventually, just for fast travel teleport purposes).

Dexterity controls your attack speed, so unless you’re playing a pacifist (not recommended for your first playthrough) it’s a high priority stat for any build.

The backgrounds that give you money or a weapon are rubbish – you’ll regret taking them by the time you hit level 2. Various “day/night / outside / inside” bonuses and penalties aren’t really worth it either. Backgrounds are mostly here for explicit min-maxing purposes, to improve key stats at the expense of the ones you won't need – something like “Miracle Operation” is exceptionally useful for the right character build.

When shopping for your new character, make sure to buy the lockpicks (it will be ages before you encounter another pair) and the Fancy Dress if female (ditto).

Even if you’re planning to play a gunslinger, put a few points into Melee and Dodge at the start. Being able to walk up to an enemy and swing something at it is far more reliable at low skill levels, and low level guns are exceptionally terrible (and you won't be able to afford all the bullets you need).

Second playthrough character ideas: Low intelligence (>5) Ogre (this game is exceptionally good at reacting to a low INT character), Gunslinger / Tech inventor. Alternately, try becoming a Master of all Skills - something I wrote a guide for, which you may want to check out:
https://gtm.steamproxy.vip/sharedfiles/filedetails/?id=818649577

Start the game with at least 9 Dexterity and two points in your chosen combat skll (Melee, Throwing, Bows - Firearms aren't very good as you start the game) - having less than two points will make the starting area a bit of a challenge.

Explore the starting area (around the Zeppelin) thoroughly. You’ll want to keep the passport, matchbook, camera (very important when you travel to Caladon) and letter (minor sidequest) you’ll find.

You'll find plenty of Iron Ore and Steel around the Crash Site and in Shrouded Hills. Save it, a person you'll meet soon (in Tarant) will be able to craft some interesting things with these ingredients. Hang on to any "Fine Hilt and Guard" items you might find or buy as well.

When Virgil suggests you access the World Map, do so. If you keep heading down the "corridor" ahead, all that you'll encounter are loot free wolves. Loot free wolves that will very likely tear you apart at this level.

When you reach Shrouded Hills, you’ll find a fellow by the name of Sogg Mead Mug hanging out at the local inn. He’ll happily join you if your charisma is at least 9. Sogg makes for an exceptionally good meatshield, and you should definitely take him along.

The Bessie Toone mine in Shrouded Hills has a Lantern at the very start. Equipping it (in the Shield slot) mitigates the penalties you get for fighting in dark dungeons / at night.

If you persuade the thieves guarding the bridge out of Shrouded Hills to leave, it's still worth chasing down 1 half-ogre lagging behind the rest and killing him. (You’ll loot a large leather armor – perfect for Sogg, and fairly rare at this point in the game).
You should find 2 stun grenades and one explosive grenade in the Crash Site cave. If the fight is a bit too much for you normally, these serve as a good equalizer. You can also drop some railroad spikes in front of the ogres before starting the fight - they will equip them, even though the spikes do far less damage than their unarmed attacks.

Even though the game suggests you rush towards Tarant, there are good reasons to explore Dernholm and Black Root before you head there (head towards the solitary ship drawn on the world map if you don't have a quest directing you there).

Lugging too much junk around? Followers can act as mules for you, but you can also deposit your gear in a random chest / barrel / whatever in any uninhabited building (but not in trash bins - their contents are automatically replaced every few days). The warehouse district in Tarant has a rat-clearing quest that gives you a perfect storage option in a fairly central location you’ll keep coming back to.

If the issue has more to do with inventory tetris than weight limits, take the largest items in your inventory and stick them into your quick-use slots.

What good are Fate Points? Personally, I mostly use them to steal stuff that would otherwise be inaccessible.

For instance, any character that uses guns or has followers that use guns could do with a Hand Cannon. And you can get one the moment you set foot in Tarant, by using a Fate Point to steal it from Sammie White – the annoying halfing spewing insults on the main street running between the entrance to Tarant and the Bates estate. Or, steal the revolver from the Gun Store owner. It does less damage, but has a major bonus to hit, which is quite useful for a low-level gunslinger.

Or, you could get the Ring of Influence from JM Morat (Grant's Tavern, Tarant) which (depending on how persuasive and charismatic you want to be) could be extremely useful. Lianna del Par (Dernholm) has a fairly good sword. Captain Wheeler (Bates factory strike quest) has a Light Machine Gun. Willy Thorndop (Southern Ashbury) has a Looking Glass Rifle. Garret Almestead, the blacksmith in Blackroot, has an axe that's like a tech/magic netural version of the Featherweight axe, with a bonus to hit chances.

Keep at least one each of the following items around once you get them: Shovel, Mithril, Molochean Hand amulet, Kathorn crystal, Heartstone (actually, you'll find a use for all 3 Heartstones scattered around the village, so hunt them down and hang on to them)

Playing as a gun/bow slinger? Make sure your ammo is in the high tripple digits, particularly when dungeon-delving. You can never be too prepared.

Even as a techie, you could do with carrying a number of scrolls. Exit, Spot Traps and Conjure Spirit prove exceptionally useful on occasion.

Tech manuals (purchased at the Tarant university) increase your expertise in Technological disciplines by an amount equal to your intelligence, per each manual. (That doesn't mean that you automatically learn the schematics you would had you learned the discipline by investing skillpoints - it only allows you to craft found schematics). Since manuals are very heavy, you want to keep them all in a container somewhere, chugging down an intelligence increasing potion BEFORE you take them out, then quickly crafting whatever schematic you want.

When you’re told to find the Black Mountain Clan, make sure you have plenty of spare weapons / good repair skills. You’re about to embark on a dungeon-delve populated by annoying creatures that break your weapons and armor. Level 20 and good battle skills are also recommended.

Personally, I used a haste potion and some glitching of turn-based combat to grab a Pyrotechnic axe schematic early. There's one you can get under Mr. Willoughsby's house (accessible via a trap door or via the sewers). The guardians will probably tear you apart if you don't grab the chest then get the hell out (you can either lockpick the chest OR plant a dynamite charge, climb out, then enter the Tarant sewers in different location to have it explode... then double back through the trap door in the house to pick up the schematic), but having a bunch of weapons (crafted via a modest investment in tech manuals) that don't break whenever they hit an Ore Golem / Fire Elemental is amazingly good.

When you're about to embark to the Island of Despair, there's a locked barrel next to Teach's ship. The contents might prove quite useful on the Island. Make sure you are level 23 before you go to the Island, as well.

If Thorvald agreed to come along, he will leave you when you talk to the guard of the Wheel Clan. Just ask him to wait while you chat, and he will stick around for some time (though depending on the patch you're using, he may leave eventually).

When you visit the Wheel Clan, pick up any Mythril you might find, and take it along to Quintara. Also, see if you can pick up a Conjure Spirit scroll before you do.

When you talk to the ruler of the Wheel Clan, make sure your INT is 14 or higher (an INT potion will help) and ask him about the Stone and Shape.

When travelling to Caladon, bring along the camera from the Crash Site.

The game has a bunch of followers you might acquire under different circumstances. The most important ones are Virgil (you've met him already) Magnus (second most story-relevant NPC, for what's that worth) and Worthless Mutt (it's a doggy! :3)

You’ll automatically meet Magnus in Tarant while pursuing the main questline. Even if you don’t keep him in the party for long, at least use his tech skills to create as many Pure Ores and Balanced Swords as you – those are quite useful at this stage of the game. Oh, and when you go investigate things while following his lead, ask him to think about the suggestion made at the end of the dungeon to earn a Fate Point.

Worthless Mutt is in Ashbury, next to the inn. Rush there the moment you set foot in Ashbury to save him. Dog is an exceptionally useful melee NPC. He doesn’t even count as a regular follower, so you can get him with any build whatsoever. However, once you get him, you won’t be allowed to ride trains.

Note - every enemy creature grants you xp for killing it, but also for every bit of damage you do before killing it (NOT per hit, but for every portion of the enemy healthpool. Easily checkable, but internet myths persist), so having your NPCs do the bulk of the fighting will slow down your xp gain. You can easily max out your level about two thirds of the way through the game, so I don't think that matters that much.

I already noted that a mage with Harm can easily break the game's combat difficulty, but here are some specifics: Pump up your Dexterity, chug a fatigue limiter (spell costs cut in half) turn on Real Time combat, and watch as your enemies drop as fast as you can click your mouse button. Get a haste potion / spell up for extra hilarity.

Another good way to break the game wide open - stealing from store owners. Find a store with an inventory you want to get your hands on. Wait until evening, and the store owner will head into their bedroom, opening the door along the way. Walk in beside them, then wait until morning so that they leave. Now pick open (DON’T use the unlock spell, as it makes a lot of noise) the chest containing their store inventory, using a Fate Point if necessary. Congrats, you now have loot levels you shouldn’t have gotten for quite a while.

Let me know if I missed anything of importance, upvote if you found this helpful. Also, I have a guide to Mastering all the Skills in the game, which might help you with any specific sidequest questions.