I actually find it a lot easier starting a new game in bannerlord, than in warband.
The trainer skill in warband required you to be higher level than the troops you're training, and the bonuses weren't all that great, they were good for up to t3 units, but you have to fight to get higher.
In bannerlord, you can hunt down looters with your recruits, you can get some more experienced soldiers straight up from the village recruitment, and you can get prisoners to join your party really fast.
Getting the recruits to t2 in the beginning does require you to lose some men, but that's pretty much the same as in warband, except that in warband, it was harder to get so many prisoners.
I usually replenish my forces from the prisoners I've captured, or just visit a few villages, and take any unit that's at least t2.