The urge to buy everything at the first opportunity can be costly to the beginning buyer of cast iron (aluminum) cookware. You need to ask yourself some serious questions and do a lot of reading of reference books to familiarize yourself with your collecting field of interest.
Resist that urge to own all the cookware, no matter its condition, size, cost, or importance to your overall view.
When you finally realize that no one else wants the damaged cast iron or that you have entirely too many duplicates and not enough of the scarce items, it's already too late.
After researching the field, you might carry an organized check list with you of the things you already own by categories and logos and pattern numbers. Maybe you could highlight items you really would like to own for helping you decide if you really need another 3 or 8 skillet, no matter how good a deal it is.
In the long run, you may have a smaller collection, ton-wise, but a better collection overall, one that will be pleasing to you, both to use and to display for your long enjoyment.