Hey BlackwaterWeed,

I think it's important to cut the variables to the minimum and just get that first grow from seed to bud. Now you may hit some problems along the way but an easy low cost start will encourage you to keep at it.

I've grown using florescent only and through the full growing cycle. I used 400W worth of light from 4 5ft 100W bulbs. I don't know what the lumen's/foot were, I just went ahead and set this up. One thing about fluorescent is that they are fantastically efficient and give out 400W of light without wasting any of that on heat. I don't think your 6x20W will cut it at an overall 120W, try getting at least 400W worth.

Use a reasonably good soil but don't sweat the details of which brand. Get some sand and if possible some perlite at the garden center. Sterilise the soil by microwaving it in batches for a couple a minutes then mix in some sand and perlite (these will help keep the soil loose and let the roots breath).

Cover your grow area in tinfoil, hang your lights on some chains and away you go.