How many plain white onesies does your baby go through ?

Ive ordered a bulk of onesies the white short sleeve ones. They came with 15 with 5 of the 0-3 months,5 3-6 months and 5 6-9 months. Idk if that’s enough or if I should order more.

My family uses them as an under garment. Like you would put the onesie on then their shirt and pants over it.