AIOs (All In Ones) are super convenient. If you have a lot going on in your life and need a diaper that comes in one piece with no covers or inserts required AIOs are a great fit for your life. I find the Bum Genius AIO's to be very absorbant and convenient. There are alot of different AIO's out there so just look around for what will be right for you.
Fitted diapers and covers are a good option as well. Fitted diapers are best known for being highly absorbent and leak less than others. I would recommend about 24 different fitted diapers and about 10 different covers so you can mix and match. Since you can reuse the covers multiple times before washing you wont need the same amount of covers for diapers.
Prefold diapers are the most basic diapers out there and while some may think they are old fashioned in this age of designer diapers, I like their simplicity. You simply fold the diaper over the baby and either use diaper pins or a snappi and put a diaper cover on. Once you get the hang of folding it is really easy to do and nothing is easier then washing prefolds. They are very economical and super cheap.
I would recommend getting a variety to start with and see what you like.
