I'd go for the 000 in Bonds wondersuits or 0000 in Target sizes for brand newborns...but they only fit for a few weeks if you have a average/big sized bubba. I think 4-6 suits would be good (although my DS vomitted pretty much non stop all day so I ended up needing more). Personally I don't like two piece suits for under 00 babies, they're too fiddly and awkward when moving bub around etc...the one pieces are much better.

I'd get more size 00 Bonds/000 other wondersuits for bubs when he/she is a little older, they are so handy and can be worn over top of each other to make them warmer even.

Singlets suits are great too, although I found them more useful as DS got older, maybe from size 00 when he started wearing 2 piece outfits.