Metal halide, T5's or CFL. If your just getting into growing, I'd reccomend starting with a few bag seeds and some CFLs if your on a budget. If not, grab yourself a MH to veg, HPS to flower. Or look into a ceramic mh for the whole grow.
I am a big fan of T5 flouros. I dont like how hot MHs get. Gotta figure out what works best for you. Hps will also work and its the best light to use if you are only going to have 1 light throughout your grow.
Welcome to RUI buddy