the clowns will fight unless you ahve a HUGE tank, same thing most likely for the blennies, not entirely sure on the midases though since they are much more docile. id say get one clarki or a pair, or you can try getting two when they ar elike quarter sized.
as far as corals and anenomes, youllha ve to wait a few months for that, but any size is okay as long as you have th elighting for it.