With the nappy. Some come in a one size fits all where you just adjust it as the baby grows and others come in set size ranges.
How many depends on how heavy a wetter the baby is and how often they do pooey nappies when they're a bit older. My DD has perfected the art of waiting for a new nappy and then pooing into it straight away

But generally they last about 3 hours before needing a change for the daytime.
From memory I started with 8 Bum Genius and 6 small fuzzibunz and then moved up to 12 Bum Genius, 3 tots bots bamboozles, a bitti boo and a bitti d'lish plus assorted boosters and we have more than enough nappies to do a wash every alternate day. We do disposables at night but that's due to lazyness really.
I think that you would save a bit on the Cloth for one baby but heaps for the subsequent ones. The initial outlay is high but personally I've found it worth it.
I think some of the stickied threads in this forum will give you a lot of start up info too.