It really depends on what lighting you have and what kind of filtration/flow you have before you can begin to select corals. Do you test for phosphate? If you are going to start corals You will need to. Make sure your water is looking good too, as close to 0 nitrate as you can. Stay away from sps
for now, most flowing corals are generally lps
(torch, hammer) remember to check the requirements for each before you buy as some corals can be aggressive towards others...