Your least expensive option is going to be prefold cloth diapers, safety pins and pull up vinyl covers. To start you out is going to cost about $20-$25 for one 12pk of prefolds, 6pk of covers, and we just used the oversized saftey pins from the sewing sections cause we could never find diaper pins. The only think you need to buy as your baby grows is the corresponding sizes of covers. This is the cheapest way. Many mom's have said this way is horrible, while I agree that it is the least convient, I don't really think it's as bad as some think if done correctly. However, I believe there is some technique involved that is often missed.
The first tip I can give is something that I have learned is a MUST when you change your baby. You must have a portable changing pad, preferably something that wipes clean, otherwise you need to have a very handily positioned changing table. Either way you really don't want to change baby on the carpet or couch or other places like that without the portable pad, poop and pee don't come out of those so easy, and once that vinyl cover is down the cloth diaper is not leak proof anymore.
The second thing you must do is have wipes and everything for diapering near by, I know some may say "duh!" but my husband did not understand this concept at first, so now I always make sure to say so, just in case others may not either.
When it's time to change baby, once you have them on the pad or changing table pull the vinyl cover down just enough to expose the pin on one side and unpin the diaper, then do the same with the other side. Do not pull the vinyl cover off until you do this. Then place you hand flat against babies back so that baby is laying on your hand, use this hand to hold the top of the cloth prefold diaper in place as you use the other hand to pull the cover off from the back side. This will avoid the poopy messes you could get otherwise trying to strip the cover down other ways and will also help keep wet diapers managable.
Once free of the cover you can check out what's going on, from hear out you change just like any diaper. Clean up poop, wipe down, powder if needed if wet to help dry off (remember no diaper rash creme on cloth diapers without using powder as a barrier, otherwise you can effect absobancy) pull the diaper up and if poop put aside for rinsing poop off before tossing in pail, if wet toss in pail. Put another prefold under baby, pin them up and pull on the cover. Good to go for another round.
This is the easiest way I have learned to deal with this method of cloth diapering, personally. For me the monetary savings makes the slight inconvience so worth it. Especially once you get the hang of it!
Feel free to add your own tips from your experience!!!