The truth is that Reining is expensive and all the advice you have been given about trainers and horses are correct. The biggest problem with getting into reining is the riders need to have skills that few other events will teach, and the horses have to have skills that few other events will teach.
You could check out IPHDA it is a stepping stone approach to developing the skills both the horse and rider will need to learn in order to eventually become efficient at reining. Using competitions at different levels to help you know when you are ready to advance your training. You will more than likely still require professional assistance to master each PHD level but since the levels are progressive it works really well for people who can only get assistance once in awhile.
How I got into reining was because of a great horse that was my last barrel futurity horse, I was running him at a quarter horse show and the timer was close to the gait ( no chutes in Canada at that time) so I ran across the timer without slowing because I knew this horse would stop and he did and left about 10" of 11's throwing dirt all over the guys at the Gait. They just happened to be there for the reining and told me I should come to a clinic for reining next week.
I never made that clinic but the next spring I did after this colt had won over $6k in barrels (1991 and in Ontario ), So in march of 1992 we both ran our last barrel pattern and attended our first reining clinic.
That June we marked our first 70 and in October we placed 3rd in the Ltd Non pro at the congress. That first year and that horse ruined me for about 3 years I thought this reining easy but then I realized it was the fact that horse was just really cool he let me make him, break him, and re make him until I finally got it right and he never held a grudge. He is still standing in my pasture I have rode a number of babies by him and they all became money earners for me. He finished his show career with points or money in 9 events. :o)
You can learn on your own but you need to have some skills as a trainer for other events and you have to get a good minded horse. :o)