First I would like to recommend a couple books that will help you, The New Marine Aquarium by Michael S. Paletta and The Conscientious Marine Aquarist by Robert M. Fenner.
Although reef tanks are beautiful they are one of the more difficult saltwater setups to maintain. They generally require more equipment, money and time compared to a FO(Fish Only) or FOWLR(Fish Only With Live Rock) tank. Reason being is coral have special needs such as higher lighting, flow and feeding. That is why a recommend going with either a FO or FOWLR.
When it comes to what equipment you need I wrote a small article on the types of equipment and a little information about each one. http://www.petfish.net/forum/index.php/topic,53881.0.html
You list either a 30 gallon or 55 gallon as the two options for the setup. Both sizes would work very well as your first saltwater tank, I wouldn't go any smaller. With the larger water volume it will be much easier to maintain stable parameters. It will also give you more options for stocking.
Now about stocking. Depending on the tank size you go with I would try to keep a low bioload considering this is your first tank. Small to medium sized fish that have peaceful behaviors would be the best bet. Clownfish are very nice, I would look into Ocellaris or Percula. They are both reasonably small, only 3-4" in length and are peaceful. You can even keep a pair if you want. The problem with some larger species of Clownfish such as Tomato and Maroon is that they are much more aggressive. Not to mention it is more difficult to determine their gender which makes pairing risky as two males will fight.
I really like Gobies and think their great fish for beginners. There are many varieties of Gobies that can be kept in a 30-55 gallon tank. They are peaceful towards most tankmates, but try to avoid mixing multiple gobies as they may fight. Blennies generally don't coexist with Gobies well mainly because they inhabit the same areas.
Some Wrasses, Firefish and Cardinalfish would work well. When it comes to keeping any animal its best to do plenty of research to make sure you are providing the best environment.
Hopefully this helps you get started. If you have any more questions just ask.