Mount & Blade II: Bannerlord

You’ll need at least 8 point for attributes and 5 focus point for a skill.


Fastest skill to level 300 is charm. Only problem it’s useless in early game

Charm

Steps to level up charm: I am listing the most first and least last

-When you win a siege as offender always choose show mercy not pillage or devastate. Keep in mind it cost influence but it’s worth it since I think this is the most xp gain for charm

-Never capture lords as a prisoner after beating them in a battle. In that dialog always pick “You are free to go”.

- destroy hideout always accept bandit boss for a duel and also when you win a battle against bandits

-Accept quest that is to protect caravan from bandit or village from brigand. Also is easy way to gain renown and influence if you’re new

-Giving gifts to lord

Xp from charm is gain by every time relation is increase .
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If I have a choice between 8 attributes toward social or intelligence I’ll choose intelligence just because steward , medicine and engineering super important to have an effective army to successfully siege and conquer. But out of the 3 skill in int attributes steward is the fastest to level . I’ll focus on social attributes after int they’re both good combine

Steward

Make sure you are the quartermaster or you won’t get xp. All you need to do is have food varieties in your inventory. To me date fruit , olive and grape are the hardest to get never sell them if you need space for inventory sell fish or grain they’re easiest to get. XP mechanic of Steward it is for every time food is consumed by your army you’ll gain xp and the more food variety the bigger that xp.

You need 8 attribute points and 5 focus in something to give it a hard cap of 302. My recommendation would be charm.

9 and 10 attribute points rank it up quicker and push it to 319/330. Helps but not needed.

As others have already stated, you need at least 8 points in one attribute and 5 focus points on the skill. My recommendation would be to use an endurance-based skill, because all three of the endurance skills are very useful, easy to grind during normal gameplay and both athletics and smithing have a high level perk that gives you one additional attribute point for endurance (also one for either control or vigor), so you should level up your skills to at least that point to get more attribute points anyway and you effectively only need to spend 6 attribute points on endurance to get to 300.

Riding and athletics both get a sizable chunk of XP every time you deal damage or kill while being either on foot (athletics) or on horseback and moving (any weapon counts, ranged and melee). It isn't super fast, but it is something you will do a lot during the course of the game anyway.

Smithing is not an integral part of gameplay and the start is a bit slow, but it becomes an overpowered money printer once you unlock the high tier parts (which you do by continuously grinding smithing activities) and your progress to gain XP and to unlock new and better parts will actually accelerate once you have unlocked parts to do high value items (i.e. 10.000 plus!), because the XP seem to be tied to the value of the items you create or destroy. Smelting really high value weapons is the best way to gain smithing XP when your skill is still low. It hurts to smelt down an item that is worth thousands of gold, but it will pay of in the long run, because you'll be able to forge items that are even more valuable and you also get high value smithing materials from them. Out of the three it is probably the fastest to grind, if you focus on it, yet the downside is that it doesn't have a finisher perk that has a good benefit tied to pushing your skill even higher than 275 (which is why I only grinded it up to get the additional attribute points and did my 300 on riding by doing A LOT of mounted kills)

One more skill that you could use for this is medicine if you want to go for the absolutely overpowered finisher perk in medicine that gives every unit in your party 1 extra HP for every skill point beyond 250. Medicine is a bit tedious to level during normal gameplay, but there is a trick how to do it really fast once you have a big party and an own settlement: Go to your settlement and move all food from your inventory into your keep's supply stash. Your army will start to starve, which the game mechanics treat as them being wounded (They don't actually die, at least not until after a long time, you can sit around and fast forward a few days until most of your troups get the wounded status without permanently losing your troops). Then just move your food back into your party inventory, let all those "wounded" troops heal back up (with you in the surgeon role yourself, obviously), rinse and repeat.