I wouldn't suggest india ink. It might be harder to clean up. Just get the cheapest ink you can find, even ink jet refill ink. Or, put some food coloring in water. Then you can clean up with plain water.
Paint clean up depends on the paint. For enamels, use mineral spirits or lacquer thinner. For acrylics, I see Windex with ammonia recommended a lot, just flush with water as a final rinse to get rid of the ammonia.
You should only need about 20 psi, but it should be regulated.
Don't be in a hurry to buy another airbrush until you spend some time with the one you have. You'll have a better feel for what you like and don't like. You may find it does everything you want.
Don