Welcome to AA!!!
Start with our articles section on getting started and cycling a SW
tank in order to ask better questions. We just LOVE those who do some of their homework in advance - as opposed to asking very basic questions without attempting to do any reading on their own.
Do not buy anything yet until you understand more. We'll help with those purchase decisions also. I'd love to see you start with nothing smaller than a 50g tank since more water is more forgiving to newby mistakes that can occur.
I always liked to recommend Robert Fenner's "Conscientious Marine Aquarist" for a starter book. Kinda old. Just ignore the part about cycling with fish. Read our articles section instead on that.
Good luck and take it slow. You'll be glad you did, believe me.