First welcome to the boards, this is a great place to learn. I would first read or get a couple of good books on the subject. The New marine aquarium by Michael S. Paletta, is a good book, be sure with any book you read that it is fairly new. New theories on saltwater aquarium keeping are always coming out and the books become outdated quickly.
You will want to decide what type of aquarium you want to keep. For a first timer I would recommend a Fish only with Live Rock and a Deep sand bed. You should get a tank that is at least 55gal. It is easier to keep the water quality stable in a larger tank.
I would read as much as you can, decide what you want to keep. then post back here when you have what you think you want to buy and people will tell you if you are on the right track. I researched for about 6mo before I bought anything.