What about a thrower on horse?
As one of the only active HTs I believe I can make a guide...
Zlisch' Guide To Horse ThrowingHorse Throwing is rather inaccurate and the damage output has been nerfed from ground throwing, heavily, my advice to you is to pick one of the maneuverable horses, steppe horse is WAY better than a rouncey for low level HTing (when I say low level I mean lvl 24 or so, until you have a real build you should just have fun leeching, or lancing, or something). I heavily advice you either bring a throwing lance (if you got 7pt) or a warspear with your gear selection, otherwise you'll be unable to do shit to HAs you've dismounted, same thing with normal archers, my tactic with archers is to facehug them in melee mode and keep on stabbing them and if they change to their melee weapon then move out the way and shot shit at them, eventually they die.
Your targets and people you shouldn't bother with: Lancers are often really easy to take out if you know what you're doing and you're on the most maneuverable horse, most lancers are still easy targets if the horse is more maneuverable, but some can be a real pain if they ride a loomed Arabian and know how to dodge (they can catch you, and dodge you)... HAs should be your main target, they're soft and so un-dodgy that your throwing accuracy is enough to hit them consistently, and they max take two throwing lances to kill, mostly one though... Archers are also good targets due to how you can just facehug them like I do, and due to riding a maneuverable horse you can turn just as fast as they can... Shielders should only be targeted if you have a clear shot at their back and you're 100% sure they're distracted... Melee players without shields can be shot at if you ride through a large crowd, but don't actually shot solo at a single one infront of you, all good ones will dodge it, and some will even camp the spot your throwing weapon hit so you can't pick it up...
I'd advice fighting lancers in a style were you ride up charging at them, throw your throwing weapon then turn for your life, you'll have a good enough speed bonus to nearly always oneshot this way (please note, I use throwing lances and 7pt).
Finally onto looting, the most important advice I can give you is ALWAYS loot your thrown weapons, if you use jarids or jav then wait 'till your target is dead or has ran, if you use throwing lances like me then if you're up against another cav get to the location as fast as possible after you've thrown, and you should NEVER bother aiming for the horse unless it's some speedy and dodgy guy on an arabian with a shield who will otherwise be able to hit and kill you.
I ain't got much advice on builds...
Hope this guide gave the info you needed, let me know if you got any questions besides why I haven't killed myself yet.