2-3 HA is good to decrease the dmg/accuracy bonus
Who/What is your main target? I used to plop around on a sumpter and throwing lances, aiming only for HA and high armoured users.
If other cav is your target, javs/jarids would be the best choice as you won't get as many opportunities to hit them. A good tactic is to hold your ground and use your horse as either a barrier or your sacrifice. Or, charge straight at the enemy cav and release just outside his lance's range. The speed bonus is going to kill him.
Against infantry, I suggest a steppe or sarranid horse, that way you can get right in their face and chuck something in it, while still being able to circle away just in case. If you're spamming into a crowd, war darts work fine. If you're really aiming at someone, javs/hvy thrw axes. The short range isn't really a problem, as a maneveurable horse will keep you alive.