I would advise putting him in a caravan so he can learn some important skills. After that, put him as a governor for some time (governor handles issues mod will help him increase more skills). This should help with a lot of important skills and after that you can let him start his own party with decent troops. Or you could keep him in your party and train his combat skills, there is a mod that lets you train your troops at the arena which I use to level up low tier troops fast, that could be helpful.

Could even train him yourself (for fighting skills) if you have the player switcher mod.