One thing I found very helpful when I started gathering cloth diapers was to buy from other mamas who were reselling theirs, so...very good used condition. I didn't want to buy or register for all of a certain kind I'd never seen before, or without checking out a variety of types of diapers.
A few places to do this are here on mothering in the sale/trade forum, but also I am part of a really active cloth diaper swap and sale group on Facebook: http://www.facebook.com/groups/ClothDiaperSwapCDS/
I liked this, because, when I started out, I wasn't sure what brands I would like, even if I could guess from other people's opinions, or the looks of something. I actually thought I wanted to gDiaper, and then I thought I'd be really into pockets, like Bumgenius and Fuzzibunz. I bought a few on the facebook forum, and from a mama I know, and she happened to add in some Good Mama diapers. They retail for like $30, but you can buy them for $10-$15 gently used, and to me they are like heaven. They are a fitted, so they do require a cover, but they have several layers, and are soft, durable, and adorable! I have gotten into wool for covers, another expensive item, running about $30 but you can find them in great condition about half off, being resold every so often.
So, now, my collection consists of about 45 diapers, 1/3 being newborn sized, mostly fitteds, the rest are half pockets (many of which I'm hoping to resell to someone on here or in the FB group) and half are fitteds from Good Mama or Kissaluvs or miscellaneous WAHM companies. I have about 6 or 7 wool covers, and about 5 more standard type covers. I anticipate when the baby comes I will really start to see which ones work for me and which don't, and eventually I will have to acquire some slightly larger sized diapers, although most of the pockets I have are one size, which should be useful.