Jessica - just a thought for you, as it looks like you are a first time mom & cd'er - I'm just going to offer my perspective, ok?
A lot of times pocket diapers, even the one-size ones, are a bit bulky on a nb. That might be ok with you, for some it works. I expect my baby to be on the small side (under 7 lbs? - I'm due in Aug!), and I think the one-size pockets would be bulky on my nb. For me, I like to have prefolds or fitteds for the newborn stage, with some good covers, and then move into a one-size diaper after the first month or two (or three). For an older baby, you probably don't need 36 diapers, although 24-36 for a nb is good.
My ds is 2 and we probably only go through 6-8 diapers/day now. And I wash every other day.
Another thought is that not every diaper fits every baby and each brand is different. It would be a bummer to buy 2 packs of 18, only to find out you don't care for the fit or style or it just doesn't work for your baby. kwim?
Just my 2 cents! Enjoy the rest of your pregnancy!