Welcome to the engaging hobby of reefkeeping!
It's really one of the most fascinating and involving hobbies I can think of.
4x65 watt power compact lighting should be enough for most corals, including popular soft corals and large polyped stony corals (aka hard corals or LPS). It's on the low side for small polyped stony corals like Staghorn (Acropora species), but those corals are more challenging anyhow and should be reserved for more experienced hobbyists. You should be fine with the four power compacts for quite some time. In the future, when you have gotten your more experience, you can upgrade to metal halides for the more challenging species.
You'll hear many opinions on what the best hang-on skimmers are, but AquaC Remora Pro will usually be one of the candidates. Others to consider are the Precision marine HOT-1 and the hang-on Turboflotor multi. All these will perform well on a 55g in my experience.
As for sand, go with 3-5" of fine aragonite sand. Caribsea sells perfect sands for sandbeds. A mixture of oolitic, sugar sized, and "special grade" sand (all made by Caribsea) will create a nice substrate habitiat. Sprinkle in some live sand after the tank has cycled to seed the sandbed and you're good to go.
Anywhere from 50-100 lbs of live rock will serve you well. It's up to you how you want to arrange it. Take a look at some people's tanks to get inspiration on how to "aquascape."
I hope this helps. You've come to the right place for reefkeeping questions and I'm sure you'll get all the help you're looking for here