Welcome to the forum Sarah. To answer your question, that would depend a lot of whether you're collecting to use or just to collect. One recommendation I would have is to get the Blue & Red books. They will help in identifying and giving an approximate value. If you're looking for users, the older Lodge (single & 3 notch) and BSR's are nice pans for the money. I'd stay away from any imports or ones specifically marked "Made in USA" as they are newer unless you just looking for a "practice pan". Doug's (this) site has a ton of great info and Doug is extremely knowledgeable. One of the best things I've done is to build a lye bath tank and electrolysis tank. Cuts the restore time tremendously. Good places to find are flea markets, thrift stores and I've had some good finds on Craigslist. Sometimes you can come across a decent deal at antique stores but I've "generally" found them to be priced too high. Some folks think if it says Griswold or Wagner Ware on it they think they have gold instead of iron.
Hope this helps,
Steve