Please list all of your parameters, as "good" for a fish might be not-so-good for inverts (cleanup crew).
And BTW, a 30 gallon tank is much more difficult to care for than anything bigger than that, so be prepared for a lot of work. Just to let you know...
Now, for the fish, you should get whatever kind of fish your heart desires (that's the reason you started the tank, right?), as long as a 30 gallon tank will be suitable. I'd say the most common fish is the clownfish (Nemo). These guys are great, and are called "clown"fish not only for their color, but their personality too. What kind of substrate do you have? Sand? Crushed coral? If you have sand, i would suggest getting some sort of goby as well. For example, the yellow watchman goby. They're peaceful, and fun to watch. He'll get along really well with the clown.
Another fact about saltwater is that you can't have as many fish as a freshwater tank. In the beginning, as your tank is establishing, you should only have about 1" of fish per every 4 gallons of water. A clownfish will be about 1" when you purchase it, and about 3" full grown, and the goby maybe 2" or so at purchase, and will grow to about 3" or 4". in a 30 gallon tank, you should really only have 7 or 8 inches of fish. IMO, you should really have only 2 fish in your tank for the first 6 months or so, then you may be able to add a third, but that's probably the max.
When you decide to finally add fish, you should only add 1 every 2-4 weeks, so your filter and LR can catch up to the new amount of ammonia from that fish (poo and pee)... lol. This way, your tank won't overload.
Hope i haven't rambled on too much!
Jenn