How do I make a sump?

[Pro Fish Keeper]

I think the title says it all . I have a 115 g (not drilled) that needs a sump. I have looked at dual overflows running into a sump then a refugium. I dont know how big the sump or ref should be for my sized tank? What type of lighting should I put on my ref? What type of tubing, adapters, control valves, pump and what not will I need? Oh and im building my own protien skimmers for the sump so i dont know how much room they will take up. Thanks for any imput.