https://www.toysrus.com/shop/index.jsp?categoryId=10872434
Check that out. It is so hard to say how many diapers your baby will go through a day. I know I changed the baby every 3 hours and it worked out perfectly, except for at night, unless he would wake, but he only woke up once a night so he was a really good baby.
Now that he is a little bit older, he is only using about 3 diapers a day. Some doctors will say to change them every hour (that's crazy).
I hope the link helped you.
Also, you aren't too early to get diapers. I am buying diapers now. I already have a stack of 4 newborns, 5: size 1 diapers, and 5: size 2 diapers. I am a huge couponer so that helps out a lot. Especially with diapers and wipes, with wipes as long as you don't open the boxes they will last a long time. I still have about 6 boxes full of wipes from when Gavin was born.