My favorite store is Urban Outfitters, even though its a little too expensive for me at the moment. I love the style of everything there. I liked it for guy clothes before I started transitioning, and I like it even more now that I'm looking in the right section.
I also really like Forever 21 because of the styles and it's super cheap. I'm not to the point where I'm shopping at the mall, so it's nice not blowing too much money while I get the sizing wrong ordering online. On the other hand, I'd save myself the guesswork and money by just trying things on in the store. :p
I'd really like to check out my local Goodwill as well. I didn't realize they paid so poorly though.