Look for Scotts Seed Starting Potting Soil. You can find it at lowes or home depot. You want potting soil with no nutrients at first. Then I use FoxFarms Ocean Forest soil when I transplant into bigger pots, it is the best soil ever fucking made for pot. Make sure you pick up some perlite too, its only like 3 bucks for a bag, and mix a lot in with your soil, like make it 4 parts soil 1 part perlite or so. Helps with drainage and keeps the soil from compacting, which is important.