I think you're doing it wrong already trying to ride a horse (especially a shitty one).
As a 10th generation cavalry lancer I can tell you what I did my first generation that has set me up nicely every since. So I've retired 9 times, and I have 9 heirloom points into items, and still have 50,000 gold (about half way to retiring on my current gen, will sell my loompoint, stop retiring, and never have to worry about money again).
Your first generation should be almost 100% devoted to making money and buying equipment. By the time you retire your goal should be to have a full set of armor that you will use when you have enough strength to wear it (talking about 2nd generation onward). You will want your weapon/s, and horse as well.
If you haven't already, use the character calculator to get an idea of what you want to be at level 30 (do a level 30 build if you plan on retiring, that usually means converting 2 skills to attributes to get you both strength and agility to a number divisible by 3). Also, decide what horse you want to use when you have enough skills to do so. I'd recommend the destrier, courser, or arabian warhorse (5, 6 and 7 riding requirement). Whatever horse you will be using, use the minimum amount of agility needed to ride it. So if you're going to ride a destrier, only have 15 agility (for the 5 riding).
http://alpha-lider19.ru/MB/ - character calculator with 100% accurate weapon proficiency model. The easier calculator to use is this:
http://infinitum.dyndns.org/crpg/calc.htm but the WPF's are not accurate (they are too high for reality).
After you retire your first time I'd sell your loompoint (for about 600k gold right now) and then buy a +1 loomed horse on the market for around 500k gold (and make 100k or more). This will give you some buffer for your next 2 generations, the next 2 retirements I'd put your loompoints into making your horse +3 loomed.
Your first generation when you're level 30'ish you might have all your equipment/gear and horse, and as long as you have 10,000+ gold (as a buffer) you can start riding your horse. I'd recommend getting your gold up to 20,000 before jumping on the horse.
I'm sure I left some stuff out, so feel free to ask if you have questions. I'll post some builds below that are my favorite, but you should let me know what weapons you plan on using. I'm assuming lancer cavalry, but will you be using a 1h/shield as well? I'd recommend maxing your athletics and power strike for every cavalry lancer build. Weapon Master is the next priority, and iron flesh is only to be used if you have extra points available.
I always used polearm/1h/shield which is nice, but I'd recommend using only a polearm (that way you don't need shield skill, and can put all your WPF into polearms).
Strength: 21
Agility: 15
Hit points: 70
Skills to attributes: 2
Ironflesh: 7
Power Strike: 7
Athletics: 5
Riding: 5
Weapon Master: 5
Polearm proficiency: 146
Strength: 18
Agility: 18
Hit points: 63
Skills to attributes: 2
Ironflesh: 6
Power Strike: 6
Athletics: 6
Riding: 6
Weapon Master: 5
Strength: 15
Agility: 21
Hit points: 58
Skills to attributes: 2
Ironflesh: 4
Power Strike: 5
Athletics: 7
Riding: 7
Weapon Master: 6
