For a newborn I'd say try to plan on having enough nappies for 10-12 changes a day. So 12 nappies per day would be a good amount as that should still leave you 1 or 2 spare most days for those times when bub does a poo 2 minutes after you put on a clean nappy LOL. You also need to factor in how often you want to wash plus the drying time (as you'll need more nappies to use on bub whilst your waiting for the others to dry). HTH.