Keep watching those old Digital Juice videos - they have a lot of good basic information, presented well. You should particularly watch the ones on lighting. Then you'll understand why diffusion material in front of the light creates a soft, shadowless light that's flattering on many subjects.
For making a greenscreen studio, you need that green to be very evenly and flatly lit, with no areas that stand out. Diffused lighting helps to do that. You light the green separate from the product or actor.
Green or blue photographer's background paper rolls are around sixty dollars thru camera supply stores.
You can get the green or blue cloth many places online or at a local sewing store, but the bolts of cloth at the store will need to be sewn together to make them wide enough for many keying tasks. Alternately, RoseBrand in New York sells extra-wide green screen material, and I find their prices reasonable. check their web site.
Cloth is light and easy to put up, take down, and transport. Paper is cheap and fragile but disposable and light. Painted walls can work if the paint is flat and you don't mind the look. If you want something more permanent, You can use the back side of vinyl sheet flooring, primed with Kilz brand latex primer and then painted, and this will make a cove without a horizon (called a limbo cove) in white or green, you can walk on and put furniture on, etc. without fear.