Since money was the primary motivating factor in my diaper choice, I went with the cheapest good diapers I could find. Note -- this is NOT Gerber -- those are HORRID. I went to clothdiaper.com, and was able to buy some "seconds" for about a dollar apiece; I think I got 3 dozen of the Chinese prefolds -- they are soft and thick and absorbent. I used the good old-fashioned diaper pins, and never had to replace them, except when I lost them, so if you go this route, I'd suggest buying at least a dozen, so you'll be sure to have them and not have to make a special purchase (plus $5 shipping or whatever) for another pair of pins. They last forever, unless you lose them.
For the diaper covers, I used the NYLON ***not vinyl*** diaper pants (I got them through TLCare.com, but you may find another brand that works). At first, I used the Gerber vinyl pants (which are HORRID), because that was the brand that clothdiaper.com stocked, and I thought I'd "save" on shipping. Even with the extra-special care it suggested (air-drying, etc.), the pants would always tear in 3 weeks or less. So, I shopped around for NYLON diaper pants, and have been greatly satisfied with them. I used diapers on both my boys for about 2 years, and only had to throw away a couple or maybe 3 pairs of the diaper pants, and that was because the waterproof inner lining started to break up and start to leak, but the nylon itself didn't tear. To compare the vinyl to nylon -- it's like Scotch tape vs. Duct tape.
One other "frugal" thing about the prefolds vs. all-in-ones or other thick diapers, is that the prefolds dry a lot quicker. I used my dryer for diapers because drying them outside made them too stiff and scratchy and my kids didn't like it; but it can take double the time to dry all-in-ones than it does to dry prefolds, which adds up on your electric/gas bill.