I own no pins. Would I be able to buy pins at WDW that represent the years I've visited WDW to include 1992, 1995, 1998? Do you buy pins that you like or that mean something, like all your favorite rides? It seems like a lot of fun but probably a lot of money, also.
Everytime you start branching out and think it is getting too expensive or hard to manange go back and reevalute your collection and see what your "likes" have migrated to.