Don't get disheartened. I know its all seems so confusing when you first start and you're trying to suss out what works for your LO. It's hard enough when you have one LO in cloth but when you're trying to use cloth for the first time on 2 I can imagine it must be VERY confusing.
From what you've posted so far it seems you have fitteds. If you need a money-saving option and what to try and use the same nappies for your new LO and your 20 month-old then you could look at buying some birth-to-potty (BTP) pockets as this way you can use the same nappy for them both - just adjust the poppers on the front. There are a lot of BTP pockets out there: Bum Genius: http://www.fill-your-pants.com/pocket-n ... enius.html, (they have just released the V4 so you can pick up V3s quite cheap and TBH there isn't much difference between the two), Fuzzi Bunz: http://www.babykind.co.uk/fuzzibunzonesize.htm and Wonderoos: http://www.babykind.co.uk/wonderoos.htm
The downside with BTP is that they rarely last thru more than one child but as your 20 month-old is likely to PT soon thsi shouldn't be a problem.