Good thrift stores and/or flea markets for graphic tees

I know next to nothing about thrifting. I'm just looking for some really nice graphic tees and have come to the conclusion that regular stores don't have what I'm looking for or have it at ridiculous prices. Tried the goodwill bins in Allapattah, don't think I will be going there again. I don't mind playing a small premium for good quality. Any suggestions?