If you are very interested in getting into equestrian photography, the best place to learn about it is http://www.equinephotographers.org
There are very high profile equestrian photographers that will give you honest critiques.
It is a funny niche and the event photography at the local level is not a huge money maker. It is enough to be worthwhile, but, you won't make a living from it.
In your galleries, your Graystone equestrian center one, you were using too short a lens. You really must use one that is 100mm or longer to keep the distortion from occuring(the big head look) And watch the feet. Can't have a horse without feet
In pleasant hollow, I would crop closer, maybe some with vertical crops. I like to crop pretty tight.
Give EPN a try, worth the money, and will improve your equestrian photography second only to being an apprentice!