Whoa! You don't put fish into your tank UNTIL it is cycled. Set up your tank with rock and sand and 80 degree saltwater at 1.024, maintain the water level, and feed the tank (not fish) a few flakes of fishfood daily until the ammonia test gives you a reading. Then see if the tank makes the ammonia disappear. THAT is the cycle.
You are quite far from ready to start: getting the RIGHT equipment involves knowing what you want to keep, and knowing what you want to keep in a 55 involves asking what will stay small enough (some species we keep reach a foot long in a year or so) to live there. Only ONE damsel of the smallest sort per 50 gallons. Clowns are an exception to that. You need a vision of what your tank will be, you need the right lights for what you want to keep, and you probably need a sump, overflow, skimmer, and you WILL need a qt tank and autotopoff.