It is kind of hard to answer the questions as to specific equipment until you know what types of things you want in your tank. Whether or not you will have corals, what types of corals, fish etc. Some things common to the needs of all saltwater tanks would be a hydrometer to test the salt levels, thermometer, test kits, salt, a good water source.
You need to decide what type of substrate you want, sand, crushed coral, bare bottom.
Decide if you want live rock as a filtration system or just a few pieces as decoration.