Prefolds are the most economical diaper choice. And really, every cloth diaperer should have some prefolds on hand - they provide a foundation to build on, plus they can be used as inserts for pocket diapers, as doublers in any kind of diaper, and as burp cloths.
Prefolds are the most durable diapers - as long as you get Diaper Service Quality prefolds, they will last through 8 children plus make good cleaning rags for another 10 years! Also, diaper covers have come a long way from 20-30 years ago, so you no longer have to use pins with your prefolds, just lay in the wrap and velcro closed. Or you can fasten with a Snappi and they will work in any type of cover.