I never did buy newborn sizes, we ended up using newborn disposables and started the gDiapers at one month. He was in the small for a short period of time, maybe 2 months (?). The good thing about the M/L/XL sizes is that the pouch and cloth size does not change. So that means from 13 lbs to 34 lbs the only thing you buy is gPants.
How do they work?