When can I start recruiting better units?
 

I was able to when I was renamed "Baron" at level 5ish. Just turned to level 14 and went back to the palace but I didnt get renamed, so I *YET CAN STILL* recruit a bunch of level 2 grunts with pitch forks. What am I doing wrong in this game?

I still use 2 units that I was able to recruit at level 1 (Royal Snakes and Inquisitors). You get new units at King Mark's castle when you become an earl (Horsemen), for all the promotions below that you just get a refill of the existing units. Your best bet for new units is random taverns and castles, not King Mark.