Well, how many gallons is it, what is your budget for lighting, and do you have any ideas of lighting? LEDs, MH, T5 HO, T5..any of these work, but I'd suggest LEDs or T5 HO (cheaper). Beginner corals would be zoas, mushrooms, softies/leathers, and some LPS (large polyp stony..type of hard coral)..pretty much anything but SPS. If you have high enough lighting and flow, montiporas are easy to keep. Corals have a symbiotic relationship with zooxanthelles, a type of algae. They are animals, but not plants even though they, in some way, carry out photosynthesis (not the coral itself, but the algae which feeds the coral). You won't need to feed the corals, but spot feeding some frozen food twice a week to LPS coral makes them grow faster.