Clothes for registry?!?! Please help!

My son (!!!!! Just found out he's a boy I'm so excited 💙💙💙💙💙💙) is due September 25th and we will be living in PA, so fall weather will have set at that point. I'm expecting a long baby, but not too heavy, based on his measurements so far and my husband and myself (hubbs is 6'11", so this kid is likely going to be tall). I have no idea how many clothes to put on the registry, and what sizes. Long sleeve, short sleeve? Pants? How warm/cool should I dress him for day and night? Do I need hats or socks? I'm like super set and informed with everything else I need, bit it just hit me I never really looked into clothes!