Seriously, outside of putting your best quality troops in the center, there is little to do but charge, and this is historically accurate from the reading I've been doing. These are slightly organized mobs going at it, with maneuver tactics never surpassing the Neanderthal 101 stage. Otherwise, you'll just need to experiment. I could not find a definitive catch all, but you are correct, with so little horse and missiles (well you might find some armies bring a trebuchet along for the festivities), rock-paper-scissors doesn't work.
Ciao, Colonel Bill