I started with newborn AIOs and then switched to OS pockets at 1 week. I have used fitteds and prefolds, too, but never full time. I do love them for at home, but I like pockets or AIOs or AI2s better for out and about.
How often do you want to wash? For a newborn, I would estimate 10-12 diapers per day, and then get as many prefolds for the number of days between washes (so if you want to wash every 3 days, I would get 36 prefolds, or maybe 40 to cover you while washing). Also, I would get a pretty fair number of covers. Probably 4-5 a day, I would think, so say 12-15 covers. The nice thing with prefolds is that you can't have TOO many

They are great for lots of things, and you can stuff pockets with them when baby is bigger. Also, I know Thirsties Duo Wraps size 1 get pretty small, they worked on DS when he was a baby, and they would extend the life of the cover for longer than a sized wrap. Hope that helps!