My ideal NB stash is just 3 dozen orange edge prefolds from GMD, 3 snappies & 6 covers - mostly Bummis + at least one wool sleep sack. Newborns are so calm and after the first week you'll be able to whip off a snappied prefold, toss it in the diaper pail, and get the new one on all one handed while nursing.
After the first few weeks in small:
3-4 pair wool longies
1-2 wool sleep sacks
~24+ GMD Yellow edge (had a crummy washing situation last time)
4 PUL covers
Once we hit mobility & solids ~5ish months on up:
yellow edge prefolds laid into covers or the new GMD snap fitteds, which I don't have yet but I'm coveting
We EC and I had problems with ds out growing the snappies before the diaper, or getting caught on my clothing so I'm just not dealing with that this time. I won't need any larger prefolds. The GMD yellow edge prefolds can last well past the first year laid into a cover trifold. I didn't even use my red edge prefolds so I'm going to get rid of most of them. Velcro always wiggled around and scratched DS so also going to get rid of that too as much as possible.
After a year, especially if you EC, you can get by with a very small number of AIO's into toddlerhood. I've been using my same 6 Bumkins for.ev.er as my only diapers.
Well that was wordy