getting down and doing it makes me learn much faster, 7 months is a long time to research without trying, but then thats just me. get it set up and cycling and you have a fair time to research stocking options etc.
20 gal has alot of possibilities
small community - clowns, small wrasses, gobys etc
sea horses - im not too sure about requirments though
frogfish
small reef
invert set up
have a look at liveaquarias nano fish good place to start, any questions fire away i leaernt quicker asking questions here then i would of reading endless about of data....