If you're JUST starting, start off slow. I've been going for 8 months, and still have avoided corals and anenomes because i've been battling high nitrates (i'm looking into building a sump / fuge to help)
Definitely start the tank off with some live sand and live rock and let it run through for a while through until the ammonia spikes and nitrites drop to 0.
To start off with, get a cleaner crew. For my 29 gallon, i have about a dozen blueleg hermits, some snails, and a cleaner shrimp. Then shrimp is really cool, he'll clean off your finger if you put it in the tank. With a 55, you can probably get more snails and hermits, i've heard some people say getting a pair of cleaner shrimp is the way to go but i'm sticking to one with my smaller tank.
Then i'd say start off with fish and stuff. I have a clown, yellow tang, and a few others and they're nice and happy. I also have a choco-chip star and a sea urchin that cruise my tank and glass.
Even without coral i still think my tank is pretty cool
I'd say get some experience with some basic fish and inverts before you start looking into corals and other stuff, they require special lighting and very very low nitrates, something i haven't been able to accomplish yet.
