Personally, I learned a good lesson during the last shortage/over priced era.
PUT SOME AWAY. That said, to start off a thousand rounds for each rifle caliber and 500 of each pistol round put me in a comfort zone. Time and cheaper ammo have slowly ballooned that to closer to 10,000 each of .22 , 5.56 and .308.
Remembering that should the SHTF, ammunition will be a source of cash to sell or trade for other necessities. Probably way too much for the short term scenario you are describing but it's really easy to blow through 300-500 rounds on a good day at the range.