I'm expecting my first soon after Christmas, so am finding out about all this for the first time too! I found the kittykins website really easy to use - and it has questionnaires to help you work out how many nappies you should need and which types might suit. Obviously they don't sell EVERYTHING, but I found it a helpful starting point anyway.
I get the impression that part of the 'problem' is that there are so many variables, and so many types of nappy out there. So you need to think about hard or soft water, whether you have a tumble dryer or an airing cupboard (I have neither), whether you care about natural fibres or just avoiding landfill, or price, or convenience, or whether you have to consider a (potentially) clueless partner / grandparent who might do some of the changes... And that's before you take into consideration the size and shape of your baby - and how much pee and poop s/he produces and when!