Newborn Items?

We have tons of 0-3 month clothes for LO but literally nothing in newborns. My #1 was less than 7lbs at birth and his little brother is shaping to be on the smaller side as well, I haven't gained any weight but he is growing fine. Should I go out and at least get a few newborn onesies? I need to get diapers and at least a couple outfits...right now I literally have nothing. WDYT?