3-1 ratio means take the first thing mentioned and use 3 parts then and second thing mentioned and add one part.

In this case 3 parts potting soil to 1 part perlite.

I find Discount Hydroponics is the cheapest. They are at Discount - Hydro. com (remove spaces) That's where I'd get lighting. They have cheaper prices if u call up and ask. I'm stuck with dialup access, so can't easily look at links, very slow.