Training for the most part is a bit broken. The most you can hope for is to get your peasant troops fully trained with a full companion troop and everyone full on trainer skill. after that you're a bit SOL and will have to rely on upgrading after battles, hiring mercenaries, rescued prisoners, or if you're evil, hire bandit parties.
TBH this is probably intended. for various reasons. doesn't change too much that training is mostly useless.
My suggestion, and this will break the game, but just get a crap ton of money, go to a village and get it at max relation while throwing the excess troops at lords for relation or to beat them for loot, and then when every time you recruit from it you have a chance of getting a large amount of the highest tier troops for 10 scillings each.