Then just buy ONE. Figure out what caliber you really need (9mm is a good place to start). Then buy that ammo as you can afford it. When you get some breathing space, I’d suggest going with a heavier caliber. But your friendly local shooting range should be able to advise.
One Ammo caliber ?
I think 9mm,
Auto pistols,
Revolvers and
Carbines.
9mm is cheap and plentiful.