well i buy one big box of diapers a month

I would start stocking up if you can. Get more bigger sizes than small but it always helps to buy lots of diapers especially if you buy them from Costco or sams club and keep all of the receipts in case your baby grows out of the small ones or in case your baby skin is sensitive to whichever ones you bought. It's just so much easier with the receipts ! You can also do a diaper raffle at your baby shower.