First of all, I apologise for my English, it's not my native language, I hope everything will be clear.
I would like to share the bonuses of the achievements and also my opinions, because these are unbalanced (yet), some of them actually really good but others definitely useless.

If a developer read this, if you have time, please read the opinions, especially the ones for the useless titles, maybe some changes are worthwhile.

Format : Title (what you need to earn it): what bonus you get
my opinion

Level 2: Maximum valour points increased by 1
Level 3: New mission
Level 4: Repair materials restore 1 additional armour point
Level 5: New mission

Totally worth it:
Seasoned fighters (100 battles won): Exprerience gained in combat increased by 10%
Bravest of the braves (100 valour points spent): Maximum valour points increased by 1
Ruthless (20 battles continued after enemy gave up): Each enemy killed increases morale by 1 additional point
Warsmiths (50 weapons forged): Forged weapons stats increased by 10%
You will get the first three titles in time, no preparation needed. The last one, however, is different, you have to make a serious commitment to get it. You need at least 650(!) materials and boring time to create 50 weapons, but the reward means you basically get a „plus layer” to your weapon.

The real problem is that since the second last update, the game has no phantom swarm, only the two hunt through. I don’t know why but that’s a huge problem. These two hunts give you about 20-30 white leathers in total. Since a normal level 5 weapon needs 3-4 of these on average, this means that if you make level 5 weapons for the whole party before you get this achievement, you won't have the leather to make new weapons afterwards. Furthermore you can’t make the best reinforced layers (reinforced layer of the…) anymore. For example, I created 5 level 5 weapon before this achieveement which is not enough for my whole team. After that I have 4 leathers left, which I can use for only one upgraded weapon or I can make one reinforced layer and that’s it.

Situational:
Opportunists (50 attacks of opportunity performed): Damage from attacks of opportunity increased by 5%
If you use this, you will get this and you will be happy. If not, you will never know that this title exist.
Tried and tested tinkerers (5000 armor points restored): Repair materials restore 1 additional armour point
Another automatically gained title, not bad, not too good.

Absolute useless/harmful:
Warriors of legend (10 might titles obtained): nothing
You get nothing…
Legion (20 companions recruited): Recruitment cost of companions reduced by 20%
If you have the money (and influence) to recruit 20 companions, the 20% offer means absolutely nothing. Also (see the white skin restriction for example) the game does not support large teams.
Enhanced layers (50 armor layers created): Armor layers removed from their slots are no longer destroyed
If you have enough material to craft 50 layers, you’ll laugh at the fact that you can exchange them for free.
Maybe a little raise to the stats like at the warsmiths or at least plus one additional stat for the layers (for example Bard reinforced layer: cirt chance +3% -> +4%, or Warrior’s reinforced layer: strength 3+ -> +4)?
Champion craftsmen (50 armor forged): Forged armor have 1 additional armor layer slot
At this stage of the game, forged armor is worth less than half of what you can buy from merchants. For example, the best light armor you can craft gets roughly +24 armor, +2 movement, and 2-3 layer slot. With this achievement, you get at most +24 armor, +2 movement and 3-4 layer slot. I don’t use heavy armors and never crafted medium armor but the situation is the same.
In comparison, you can easily buy from merchants these kind of armors: example[imgur.com]. That is almost double the amount you can craft! Make no mistake, you need them for winning harder battles.

Maybe need another level of armor crafting in the compendium or scaling with the blacksmith skill to compete with (or to outrun) the merchants but at this stage of the game, the armors you can craft, unlike weapons, are necessary at level 1-2 and completely useless from level 3-4.

Not know (yet?):
Elite killers (5 champions killed): Need more region
Expert rackers (10 successful hunts): Need more region
Providential liberators (20 locations freed): Need more region
Ravagers (5000 units killed): ?

Level 2: Possibility to negotiate missions in the list of bounties
Level 3: New mission
Level 4: Increases by 1 the number of contracts you can accept in the list of bounties
Level 5: New mission

Totally worth it:
Untouchables (2000 krowns earned by delivering prisoners): Turning in prisoners also grants 20 influence
I have practically finished the game on both normal and hard difficulty and my opinion is that especially on hard difficulty, the easiest way to make money at the beginning of the game is to sell prisoners. In fact, the level 1-2 battles are easier because you can capture somebody at half life with one action but can’t kill him. Basically the first 60 krowns I spend is for chains. If you get influence for it, too, that is amazing at the beginning.

Others:
Reputable mercenaries (2000 krowns earned through missions): Krowns gained from missions increased by 10%
Skillful merchants (2000 krowns earned through trade goods): Selling trade goods at a higher price than their reference price also generates 2 influence
Reliable retailers (10 trade missions completed): Sale price of trade goods increased by 10%
Weapon dealers (2000 krowns earned by selling weapons): Sale price of weapons increased by 10% per quality point
Armour dealers (2000 krowns earned by selling armour): Sale price of armour increased by 10% per quality point
Resolute resellers (1000 items sold): Sale price of all items increased by 5%
Investors (100 trade goods purchased): Purchased price of trade goods reduced by 10%
You get these (or some of these) in time and all of them are useful but none of them worth the grind for it. I think you can get too much influence and money in the later stage of the game if your party is good enough, but that’s not a big problem at this moment. Perhaps this will change when the level cap disappears.

Absolute useless:
Upstarts (10000 krowns earned): nothing
No title (1000 krowns earned in scenario missions): nothing
Golden touch (10 trade titles obtained): nothing

Not know (yet?):
Masters of luxury (2000 krowns earned through luxury items): ?

Level 2: Access to assassination missions in the list of bounties
Level 3: New mission
Level 4: Access to the black market and its agents
Level 5: New mission

Totally worth it:
Backstabbers (100 enemies killed with attacks from behind): Critical hit chance during an attack from behind increased by 5%
Every way you can increase your damage is worth it.

Situational:
Dead or alive (100 hours spent being wanted): The suspicion meter depletes 15% faster
Sticky fingers (300 stolen items): Suspicion reduced by 15% during a theft
Poachers (15 animals captured): Chances to capture an animal increased by 50%
If you steal often or if you use animals, these are useful for you.

Absolute useless:
Lawless (30 battles won against the guard): Influence gained after a battle against the guards increased by 20%
Master assassins (10 assassination missions completed): Completing an assassination mission also generates 20 influence
After some time you get too much influence, you don’t need more.
Ruffians (10 prisoners recruited): Recruitment cost of prisoners reduced by 20%
The 20% offer means after recruiting 10 prisoners, the next five you recruit cost just four. Lol.

Others:
Shameless (20 battles won in ambush): ?
Highwaymen (30 battles won against merchants): ?
These two seem buggy. In the penultimate update they did something to the line of sight, it just disappeared, so you can't ambush anyone. Exactly when you start a new game, you can ambush someone once, then never again. And the other one is strange because I've killed several refugees or traders, wanted or not, but I still see 0/30.

Hoodlum (10 battles won alongside outlaws): ?
Pony thieves (5 ponies captured): ?
I don't know exactly how to achieve these, when a battle is considered appropriate and how to catch a pony but I’m curious because they seem useful. I would be glad if someone could tell me.

Profilic fences (200 stolen items sold): ?
Crime lords (10 crime titles earned): ?

Level 2: You can craft the Lectern
Level 3: New mission
Level 4: New mission
Level 5: Coming soon

Totally worth it:
Collectors (20 knowledge from the same category of the Compendium learned): Immediate gain of 2 knowledge
Local heroes (1 region completed): Completing a region also grants 1 knowledge
Eclectic intellectuals (5 knowledge learned in at least three different categories of the Compendium): Immediate gain of 2 knowledge
Every way you can get knowledge is crucial.

Situational:
Versatile craftsmen (8 professions discovered): Experience gained for each profession increased by 10%
If they delete the current cap for professions and you can upgrade „companion”, it will be important, until then it is not relevant.

Others:
Exterminators (10 rat nests purged): Need more region
Encyclopaedists (100 knowledge acquired): Need more region
Archaeologists (50 antiquities studied): Need more region
Explorers (100 locations discovered): Need more region
Keen amateurs (5 categories of the Compendium discovered): Need another category
Seasoned scholars (10 knowledge titles earned): Need more region

Truth seekers (10 secrets discovered): ?
I don't know exactly how many secrets are in the game at the moment, I found two, maybe there are 10 in total, maybe they will be added later.

Tomb raiders (25 Tomb of the ancients explored):
Lords of the roads (25 regions completed):
These two titles are too ambitious unless there is a full region in the game that contains nothing but tombs instead of a city, rat's nest, , mill, etc, or unless there are 22 more regions, they can never be completed.

This is my first guide, I very much welcome criticism, but please, if you don't like something in it, don't just say "it's crap", but rather "it's crap, it should be like this".