First you will need a membership at Aquarium Forum, which you already have
Seriously, though, you'll need a high range ph test kit, a jar of marine buffer, a salinity meter, and synthetic salt (if you will be mixing your own water). As far as filters go, you can use the same filters as freshwater, but also consider a good protein skimmer. The skimmer foams the waste out of the water and puts much less of a load on the other filters. A 55 gallon tank has a good success rate with people that dont fall out of the hobby, it makes it easier to keep things stable vs having a very small tank. Basically you want to go with the biggest tank you can because the mistakes are mitigated and the temperature and other things don't fluctuate as often. A 75 gallon tank gives you a much better palette to create landscaping and stack rocks, etc. Go with a 180 if you can!
You can use the same maintenance tools as your freshwater systems, so you probably have most of what you need already. Same goes for dechlorinator and other simple things you already probably have laying around like nets and such.
Also consider getting some good bulbs to bring out the colors and perhaps paint the back of the tank blue or black (or use the film) if its going up against a wall.
Remember to start slow because when you are cycling the new filter, the slightest amount of ammonia is much more toxic in the saltwater (high ph magnifies the toxicity of ammonia) than in the freshwater you are used to. So don't overfeed and don't overstock the tank at first. Patience will be a virtue. Also ask a LFS for a dirty piece of their filter to seed your system with good bacteria once you get your cycle going, or use the commercial bacteria available on the shelf.
Regards
