Riders will increase their efficiency in showing in a particular discipline the more they enter. A bonus will be added to their player points calculation in the shows based on the % of their skill. Basically 100% riding skill would double their player points earned in a given show.
Adding Xp to horses
Riders can add Xp to horses by training them in their barn. This is based on the skill at adding Xp, the monthly limit (which is based on player level) and the level of the horse being trained as to how much Xp can be added to any given horse.