If you want results, I would go with flourescents in the 5500k to 6500k spectrum range. If you are actually trying to grow a garden without any window light, I would suggest using high power flourescents which put out a high amount of usable light for their wattage. If you are trying to provide light for a 20 square foot area, I would suggest a HPF system of at least 300watts consumption which should bring you up to about 20,000 lumens of light. I'm talking about the lights that hold 3-4ft long bulbs and at least 4 of them.
I use a 70watt=350watt cfl bulb which is enough to support 5 houseplants along with window light and it seems to be working, but if you want actual growth I would suggest HPF.
Don't be tricked by those little cheap blue bulbs because they eat a lot of wattage and don't give off much light, and the led UFO lights that are 90watts, or 300watts work, but not any better than flourescents and they cost a lot.
I've done my research on plant lights.