I would suggest first researching SW
fish on sites like liveaquaria.com, bluezooaquatics.com, saltwaterfish.com. Find fish that you think you just MUST have, then look to see what size tank the site suggests for those fish. That'll give you an idea of how big a tank you should go with, and that's the first step to buying a tank!! Once you have a list of fish that you think you want, open a thread under "Saltwater getting started" and tell us your list. People on the site will let you know of any incompatibilities in your list and you can hone the list from there.