The best way to increase salinity is to use salt water instead of fresh water when you top off your evaporation every day. When you do water changes, you can also add new water that has a higher than normal salinity. The important thing is to increase the salinity gradually.
You can add some hardy corals now if you want. Some good ones to start with are kenya trees, leathers, mushrooms and zoas. These are not demanding as far as water quality and lighting go, and they don't need any special feeding attention.
A good clean up crew consists of a variety of animals. You definitely want snails, I prefer a mix of turbos, astraeas, conches, nassarius and trochus. You can get hermit crabs if you want -- I don't like them because they will end up killing your snails for their shells. You could get an algae eating crab like an emerald crab, they are cool. A cleaner crew usually consists of some shrimp too, like cleaner shrimp or peppermint shrimp. I would wait a bit before adding shrimp though, they require a more stable environment than a brand new tank. Also, you could get a starfish, like a brittle star or serpent star. Those are two of the hardiest and best at cleaning up detritus on the substrate.