primers help foundation apply smoother and last longer. its especially ideal if you have flakey skin or large pores. primers help fill in the pores so they look reduced when you apply your foundations and concealer on top of it. i like to think of primers as a way to create a smoother canvas. if you have good smooth skin and non-existing pores, it might not be as neccessary except help your makeup last longer.

personally, im still experimenting with primers. i do not like monistat because it causes discolouration on the skintone. i am nc25/nc30 and very peachy. monistat dulls my skintone and makes me look kinda grey. primers shouldnt change skintone... but the good thing about monistat is that it works very well to fill in pores.