I have done all of the above, thrift store, Goodwill, Ebay, sales racks. Then recently bought one of those thingeys that attach fake gems and my daughter is working on fixing both jackets and tops. Oh my daughter is the one that shows the most. Now last year at AMHA World I did buy her a very nice formal style jacket, a bit longer than I usually get, but it was half price, still expensive, but she needed it to show at night.
Its the same way with pants, Goodwill usually have some great deals. As for tops under those jackets, she usually wears tank tops because its cooler in the summer months and in the ring. Plus for a smaller price she can wear alot of different colors that way.