I'm don't know alot about BunGenius diapers, but usually it will say of they are a "one-size", which means birth until around 22lbs. Keeps in mind, "birth" usually means around 8lbs, so if you have a little baby, they might be big at first. I personally don't like AIO (all-in-one) diapers, because I find they slow the washing and drying process some. If that doesn't matter to you, they are the easiest, because you only need one item! I strongly suggest flushable liners, which make messy clean-ups so much quicker. You'll also want a good diaper pail, since there are no chemicals to keep the stink down like disposables, and most importantly, get a good wet bag to keep dirty diapers in when you change them on the go. Nothing like having a stinkly ziplock bag open in your diaper bag! For the diapers, go by what you can afford. If you don't have alot of money, pre-folds, covers and lines. If you can spend a little more, nice AIOs and liners! You'll need alot at first (10-15) unless you want to do laundry twice a day, or interchange with disposables. Hope that helps some!