you need to decide what kind of tanks you want before deciding on fish. some fish are reef compatible, some are not.
ocellaris clowns go about 3.5 inches max. perculas are a little smaller at full size.
Reef Fishes by Scott Michael or Marine Fishes by the same author give LOTS of info on potential fish you would be interested in.
Its not so much a matter of hard to start a reef, but a determination to be patient and do a LOT of learning, and be willing to work LOTS of overtime to get the right equipment the first time. Otherwise, you'll start with LFS info and buy crap u'll just end up not using. Then u'll go with the better stuff. So in the long run, its cheaper to spend the big bucks up front for the good gear.
hth and Welcome to the Boards!