So I think about diapering my next newborn all the time, so I can be ready and never have to use another disposable. I also plan to previde my sister-in-law and my best friend with their newborn stash, assuming they will cloth diaper as well (fingers crossed!). Remember, one-sizes are supposed to fit babies from 7-35 lbs. Sometimes that is not the case, depending on where your baby is chubby the most. The biggest problem is when there are gaps between the diaper and the baby's thighs. So here is what have came accross, heard other mom swear by, and seen tried on.
12 Thirsties Duo Wraps Size 1 or 2
24 Green Mountain Diaper's Clotheez Orange Edge Prefolds
(can use later on, trifolded in one-size covers)
(if you can catch one of their seconds sales that would be best)
3 XS BumGenius AIO amd 3 Happy Heiny's Mini One-Size
(nights and long car rides diaper)
I have great confidence in these products, after time and time again I heard great reviews from cloth diapering moms who started from the beginning. All together (at retail price) this stash should cost around $276. You figure that when your little one reaches the weight needed to get to a size where they can use one-sized cloth diapers, your little one would have already used 500 disposable diapers (assuming they have only 12 changes a day for 6 weeks) and that many wipes (if not more). All together this would cost $200 easy, and you would never get to re-use it again or your baby would not have as fluffy of a bottom.
Items you will also need (that will last you until potty learning) is a 13 gallon trash can, diaper pail liner, a wetbag (for travel out of the home), cloth wipes, cloth diaper safe detergent, and snappi's for the prefolds. All of these items, including the diapers, can be found at discounted prices through "for sale or trade" forums, seconds sales, and from WAHMs (work at home moms). For example, BumGenius have seconds sales every once in a while and they go for around $10 (XS AIO). That's a savings of $3 per diaper, so you catch my drift. Another way to save money is to pick an online store with free shipping, like http://www.cottonbabies.com/ and http://www.mamisandpapis.com/, and catch them during a sale!