I'm a finance manager and did AAT, I did level 3 whilst I was temping in a bank and level 4 once I had a finance role. If you have a basic knowledge of finance and numbers it's relatively easy. It was quite a while ago but I think I skipped level 2 as I had done accounting at a level
I manage a few aat folk - if at all possible skip level 2 - its very basic - level 3/4 offer more value to you and an employer. If you have level 3 then that is good for entry level jobs (although we hire folk without and part pay for thier training) which might be an option if you have some experience and would give you the chance to see if you like the type of work.