Well back to your original question. When only keeping fish the important tests are pH, ammonia, nitrite, nitrates, salinity, and temp. You'll want to keep pH between 7.8-8.3, ammonia 0, nitrites 0, nitrates keep as close to 0 as possible, salinity between 1.021-1.026 and temp 77-82.
When you start with corals I would suggest starting with easy to keep soft corals. You won't NEED to add any extra tests for them but your salinity should be between 1.024-1.026.
When you feel more comfortable with corals and want to try hard corals you'll need to add calcium, magnesium, alkalinity, and phosphate tests. Keep calcium 380-450, magnesium 1250-1350ppm, alkalinity 7-11 dKH, and phosphates 0.
Hopefully this is more what you're looking for.