$20 Build a Better Athlete. It has (I think) 20 exercises in it that will help you build the necessary and balance and muscle basics that you and your horse will need to progress into whichever discipline you choose. I found it very helpful for suppling my horse.
Basically with young horses, your goal is to get them balanced and build up the proper muscles so they can use themselves effectively. Let your horse tell you each day what to work on. Sometimes they're stiff, their transitions stink, they're nutty, etc. Whatever he gives you day to day, that's what you work on. If you can get him out on trails, that will go a long way toward building up the muscle he'll need to do proper flat work and jumping.