There is so many brands of soil out there, picking the best one will be a difficult task. Just get some "potting soil", with added vermiculite, sterilized soil. I pick up big bags at Wal-mart for like $5, and I can grow some pretty potent buds.

Only water when the soil is dry. Dip your finger in the soil, if it's moist underneath the top soil, don't water, if it's dry, water. I water only twice, maybe three times a week. Good luck!