Try and find out how the breeder grew the seeds and mimic their style. Soma uses Advanced Nutrients, Subcool uses his own mix with Roots Organic as the base, and Mandala recommends using any good premium soil such as Miracle Grow, Kellogg, Supersoil Potting Mix, or Sunshine Mix. I'm a big fan of Kellogg, which runs $5 for 1.3cu bag at Home Depot. I don't buy into the $$$ = better soil, but to each their own. The most important thing is to understand what you are using and learn the needs of your plants. What works for me may not work for you and vice versa.