I'm not sure where the best tickets are, but one thing I can tell you is make sure they are official. Disney tickets are nothing more than a piece of cardboard with a magnetic strip on the back. There is no way of knowing if they are good or not. Every 7-11 has a ticket booth outside of it, but usually those involve a 5 hour time share presentation, and I have read reports where people are rewarded with expired tickets!
Buyer beware, do your homework!