salinity is ideally at 1.023-1.026 some have it lower for FOWLR
and some have it higher for reefs. Chromis are great starter fish. Cheap, hardy, peaceful, reef-safe, and they are pigs! (or at least mine is haha). Clownfish are usually hardy also. I highly recommend staying away from damsels!!! Even though they are hardy and cheap, they are very aggressive and very difficult to catch. Many say they become the bullies of the tank..picking on the newcomers. Definitely add the more aggressive fish after you've added all your other ones, but even then, I still wouldn't recommend a damsel.
Beginner Fish: Tropical Fish for Beginners in Saltwater Aquariums