People have given you alot of good advice but I’ll add my two cents on top of what others have said:
Don’t count out TBs. Some are calm and wonderful. But not all, so be picky about who you look at.
Don’t count out ex-broodmares. There are some very talented 7-13 year old registered warmblood broodmares that are wonderful and pleasant amateur riding horses that can be purchased for $5-10K. They can be cheap because they don’t have a solid show record or much training. But sometimes the breeder is scaling down and it is cheaper to “firesale” than keep the horse at the barn if they’re not going to be bred.
Don’t count out Arabians, morgans, appendix QHs, paints, draft-crosses, etc. Some are very very nice and very talented for lower level…sometimes even upper level…dressage. you can sometimes find a western pleasure or trail horse drop out who is a drop out because he has really nice expressive gaits. You can sometimes get good deals on these horses.
Don’t count out any horse that needs a good home. Network! Sometimes very talented, very pleasant horses have owners who fall on hard times or develop health problems and they’d rather their horse go to a good home for cheap than a bad home for a good price. I know many MANY people who got nice horses this way.
Good luck!
J.