For a refugium with macroalgae, having the lights on a reverse cycle from the main tank, or having them on 24 hours a day (like us lazy people do), is ideal. It will help to keep your pH balanced, and 8 hours opposite of the tank lights is fine.
A cheap fuge light is just a regular freshwater strip light you can get from any pet store. Algae does not need a lot of light to grow.