I have a 12 gallon gl fishtank, I want to convert it into a saltwater aquarium, what exact items do i need?

I have an 11-12 gallon gl rectangle fishtank, i want to convert it into a saltwater/reef aquarium. What exact equipment do i need? as in brand and name of the items, because i want to buy them online, because i know they will be pretty expensive at the fish store. THANKS!!