You don't need liners until bub is on solids unless you are using nappy rash creams
I've tried a bunch of different brands and I think bum genius are brilliant. Definitely get a couple of them to try. They fit my toddler and my newborn - most one-size fits most (OSFM) don't fit my toddler anymore.
If you are interested in second hand nappies join the Facebook group "but and sell your MCNs" but I've found if you buy new nappies on special they aren't more expensive than second hand.
Also My Little Ripple from eBay are cheap as and they are a great stash builder. They work brilliantly and only cost around $4 a nappy.