The calibers I buy in case form are the usual 9, 40, 45, 223, 7.62. I'm going to add .380 to that list shortly because I picked up another machinegun that shoots it.
This is also an important consideration.
Those of us that shoot full auto usually look at ammunition accumulation differently than those who shoot strictly semiauto or bolt action.
When I take full auto out, it is not uncommon to go thru 1000 to 2000 rounds at a time.
While most people look at buying boxes of ammo, Class III shooters usually look at buying by case lots.
Of course, that being said, even when I don't shoot Class III, there have been times when just pistol shooting I've gone thru 500-1000 rounds in a single range outing.
Dave