Just From http://www.sunflowerbaby.com/newborn/
A typical newborn gets around 8-12 diaper changes a day(again this depends on many factors). As the days pass and they are able to sleep through the night the amount of diapers used changes to 6-8 per day. For this reason coupled with the fact that the baby is growing you will have to balance out a way to buy diapers. It is advised that you start out with the small size first but it is overkill to buy a lot of diapers at first since the baby might outgrow them even before they are all used up.