hmm....I know anemones are pretty tricky, from what I hear...I may be wrong, though. I don't like anemones, I have had BAAADDD experiences with them, but that is just my opinion. You don't need the anemones for captive clown fish, but you could to an anemone only tank, if you would wish. The biggest tank you could afford would be best. The kind of skimmer you would put on a 10-20 (CPR bak-pak or Red
Sea Prizm or something like that) could be used on a 30 gallon, too. As far as lighting goes, get whatever you can afford, because you'll probably want to upgrade in the future, anyway. You could go PC or VHO, I have seen/had good results with both, even on acros and other
SPS corals. The difference in price won't be TOO drastic between a 30 and a 20 gallon, and the care is basically the same, time-wise. It is really a matter of personal taste, and absolute budget!
HTH.
btw-welcome to TRT!