That gelding is a good example of what to look for.
Regardless of having a trainer that you would buy through, I think it's good that you are educating yourself in what makes a good reining horse. Trainers can be great when horse shopping... but its good for you to know what you want, recognize what you are looking at (the good points and bad), and be able to say no when its not the horse for you.
You should probably start with assessing your needs and goals. If you are like most of us, what you want will be far beyond what you actually need now
If you are new and just looking to start, an older finished Reiner is worth considering. They know how to do it right, and you can learn the ropes correctly without trying to teach yourself and the horse at the same time.