"The Conscientious Marine Aquarist" is a very good book to begin with. Get the book, read it, digest it, and then begin planning what sort of tank you want. In saltwater aquariums, bigger is better. Larger quantities of water are more stable, so you'll want to get the largest tank you can afford and that you have room for.
After you have read the book, you will have a better understanding of what equipment to get. One thing is for sure, saltwater ain't cheap.