I have cloth diapered 3 kids and here is my advice and experience.
Get some easy diapers. Don't obsess over squeezing every last dime and think you have to get prefolds. Yes, they are cheaper, but any cloth diaper saves money over disposables, and if you start with easy diapers, you are more likely to stick with it. My dh didn't really get on board when I started with prefolds; when he saw the FuzziBunz he liked them and started to use the cloth.
Have some newborn sized diapers on hand before the baby arrives. Even if they end up not fitting for a long time, someone else will gladly buy them off you, so you will not lose money. Diapering a newborn in sposies costs over $200 for the first two months!!!!! My dd wore her newborn dipes for 2 months and I spent less than $200 on them, so I made out.
Good and popular newborn choices: Kissaluv 0s with XS Thirsties, XS BumGenius! 3.0 All-In-Ones, XS FuzziBunz, XS SposoEasy AIOs. Round out your stash with some infant prefolds and XS Bummis covers. You want to have 30 newborn diapers total.
You will use these diapers for a couple of months and then have a good idea of which you prefer. Then you can buy either more of the diapers you liked in a larger size, or try some of the one-size diapers. The most popular one-size diapers are BumGenius! 3.0 One-Size (pocket diaper), FuzziBunz One-Size (pocket), BumGenius! Organic Cotton One-Size (AIO) and the new Gro Baby organic cotton one-size system. These are all popular diapers, so if you don't like any of them, you will be able to sell them easily.
