@ShiningStarz I'm no expert as this is my first, but we got a little tutorial from SiL and I've done quite a lot of reading so happy to share what we've found out. I'd highly recommend www.thenappylady.co.uk/ - there's a whole section with advice and also a shop on there that's quite comprehensive. You can also apply for vouchers from the government or local council in lots of areas, we got £54 through www.realnappiesforlondon.org.uk/.
To use them full time we're going with 20, and we're slowly buying that number in the newborn size and then in the one size option. We've been lucky to get lots of newborn ones second hand.
I think you need to wash most of them after each use. You can get different types though - all in ones where you just sling the whole thing in the wash, those with detachable liners that you separate then wash and some that have a completely separate inner that you wash each time and a wrap that you might not always need to wash after every use.
My SiL said that you only really need the compostable liners once they're weaned and their poo is more solid, then you just take out the papery liner with the poo and flush it down the toilet. Otherwise she doesn't bother to rinse, but I guess that depends on preference.
We've started washing some of ours to improve the absorbency and they do take a while to dry - on the really sunny warm days last week they took most of the day. I think they'd be ok indoors with the heating on or a dehumidifier but would probably take a good 24 hours.
You can buy these waterproof zip up bags to pop dirty ones in and apparently that stops the smell from getting out and apparently they don't really have smelly poo until they're weaned anyway, but again, no first hand experience here!
Hope that helps!