You might as well run 4 plants in that set up. You could also save some life expectancy hours on that light by using some compact floro lights until week 5 or 6. Just my opinion. Good luck.
I've had good luck using a basic organic potting soil/mix from Lowe's and mixing in Plant tone and Chicken dung. Then throughout veg and flower stage use molasses and Neptune Harvest Fish emulsion...The yellow bottle I think it's 4 2 1