I am cding my 1 mo adoptive son. He was born prematurely at 36 weeks. He fits best in a first class baby 0 with an alexis featherlite pull on cover (preemie size) or little lambs aio size newborn. Lots of newborn sizes fit my 7 lb baby though, too. I have kindhearted women small (which is listed on granolamoms as newborn), kissaluv 0 (easy to find), baby luv small (which is too big for this baby, but worked fine for the previous), preemie prefolds, nanipoos newborn fitteds (my majority), and small or newborn not sure valor kids (similar to mollytogs). For covers I have proraps, bummis snap, stacinator newborns, and a few aios for doctor visits.
If I were you, if you plan on cding from the start, prorap newborns have leg gussets and preemie prefolds fold right in. No pins required, and fairly inexpensive. I would get a few xs or newborn size aios for doctors appts as you will be going to them frequently. I like fitted diapers with pull on covers or stacinators if you have more money to spend. They keep the runny poo in really well, and small diapers don't have much fabric to absorb with, so I think they are more absorbant than prefolds. I have some snappis, but I still haven't used them much. I have never pinned.