I just reload for the guns I shoot regularly, in calibers that cheap ammo isn't available for. When I shoot store-bought ammo for the other ones, I always save the brass until I've aquired enough to make reloading that caliber more attractive. Once I have enough brass that would about equal what a set of dies would cost me for that caliber, it's time to start reloading that caliber instead of continuing to buy loaded rounds. That's my system to determine if I'm shooting enough of a caliber to warrant reloading it. I've been shooting for long enough that I currently reload for every caliber I own, but that was the process for determining the order, more or less, of which caliber would be the next to start reloading for. I don't know if that makes sense to anyone else, but it's worked for me over the years.