Best advice I can give is go slow, do tons of research and test your water often with good reliable test kits (at least until you have everything dialed in). I came from freshwater myself and now I have a full blown reef. Ask as many questions as you need, but before starting a new thread do 5 minutes of research to your question (Google is easiest). Last advice I can give is take what people say lightly, many people answering questions have there own way of doing things, and that isn't necessarily the way that will work for you and your setup.
Now for an equipment it depends on what you want to do with the aquarium. Do you want fish, corals, both? What size of tank do you want? Also species will have their own requirements.
Tank (let us know the size)
Stand
Auto top off (keeps salinity constant)
Sump (optional and nice to have)
Heater (something reliable and properly sized)
Protein skimmer (helps remove organic compounds between water changes)
Biological filter media (can be as simple as the rock you use in the tank)
Chemical filter media (Carbon)
Mechanical filter media (pads or socks)
Marine salt
Sand (1.if you want it and 2. If any of your creatures require it)
Water pumps (for circulation in the aquarium and return from sump)
Lighting (type and power depends on what you plan on keeping in the display)
A quarantine tank (most important in my opinion, to help avoid introducing disease and undesirable hitchhikers)
RODI (for filtering water coming from your tap water supply) this is easier and cheaper than getting water from the aquarium store.
Teat kits (start with a refractometer, ammonia, nitrite, nitrate. After that, if keeping coral you will need calcium, alkalinity, magnesium.)
I may have forgotten something but this is the minimum I would personally start with. You will end up getting a lot more stuff than this once you are up and running and depending on what you plan on keeping. Best of luck.
