I have about 6-8 of each size onsies but a ton of dome up singlets ( I think you guys call them something different in America; I'm in NZ) I prefer lots of singlets as they are what the poo and pee hits first If there is an explosion!!
This is number 3. I would say 12 each to be safe. Several spit ups and bow outs in a day or two and you have a naked baby if you don't stay on top of constant dirty laundry.
Re: How many??