That's easy! One for my team set, one for my player set, one for my type card set, and one for each miscellaneous other grouping I might be working on, plus trade bait or items for sale (that I may never actually sell). That's at least 5 right there. Also need to take into consideration whether there are different front/back combos, variations, or proofs known to exist, in which case you multiply each possible card by 5.
Any more than that and your just a hoarder.
