Soil and fertilizer are two very different things. If you don't know this you are probably not ready to grow. I recommend at least 40-60 hours of reading and researching before starting a grow. Purchase a cannabis horticulture book, Greg Green and Jorge Cervantes write excellent grow books.
Your fertilizer is typically a liquid solution you feed your plants with when they are dry. Not all growers use fertilizer in the first month of growth because soil (happy frog) comes with a limited supply of fertilizer in it. Please observe at least 2 grow journals all the way through and you will understand. Try and replicate success and avoid any and all advise from ghetto growers. Not all grow journals are good examples. But in speaking off success, Technaflora sells a complete and very inexpensive fertilizer kit that seriously kicks ass. "Technaflora's Recipe for Success Kit" is only 35 bucks for everything you need for your first grow or 2.
Edit: took me a minute to realize I'm in organics. Fucking half my info is wrong now. Not all organic fertilizers are liquid, and technaflora is not organic. BioBizz is organic, however. BioBizz sells an affordable and complete starter kit too, but I do not know the price. BioBizz is another example of liquid fertilizers. Also look into Roots Organics, GeneralOrganics, and Organicare's liquid fertilizer. I've used all but Roots Organics, which I hear is absolutely amazing.