I have about 30 newborn diapers and about the same in rotation of our one size for DS. When DS was a newborn I would change up up to 12-18x/day depending on how often he pooped, if he pooped on the new diaper after I removed the dirty, peed on the new diaper before it was on, etc. I like having extras as you never know if you will have a CS or something else that may make it hard to wash daily. Having 2 doz one size diapers in rotation at 3+ months worked fine for us (but I am addicted and have more like 50 or so. I plan on using them all for this LO and the next if we are lucky :) (hope to use the same diapers for 3). As a toddler you will find that you change them less frequently as they PL and learn to hold it more.