Been playing these guys a lot with Imp Armor + Bow. If you're fighting a lot of heavy cav you'll stand no chance on horseback, but you can dismount and use them as the only spear-equipped archers in the entire game, with decent armor and a good sword. If you're fighting anything else just harass, look for out-of-position units, fire all your arrows as quickly as possible then charge with the inf. Also fun to just stand inside your infantry formations, since they can still have line of sight to shoot from horseback.