Love your collection! Vanellope really is the cutest.
I'm in the same boat with buying only pins I like. I've gotten a lot of great, authentic pins on ebay, but I've never been one to buy lots. I have a few sellers I follow on there that I trust and those I haven't heard of I do a lot of research on forums and google. If that doesn't yield any results, then I try to go by their ratings.