Working toward keeping a reserve of 1000 rounds of every caliber I shoot. That covers .38SPL, 9MM, 5.56, and 12 GA.
So far I've only got it for 9MM and 5.56 but those two are what I shoot the most. 12 GA should be easy because its cheap and .38SPL, well I dont shoot it real often so I typically buy some with each range trip when I buy for others. The leftovers are kept and more is bought next time.