I just throw a fairly decent amount of seeds .Then hope they grow outside .An wait on the rain or just water it sometimes depends on how I feel if they never come up .I'll wait a while then throw more seeds .I buy from a good seed seller who isn't greedy and gives plenty of seeds. Buying soil isn't even necessary unless you live in a desert or something. I just buy pots to grow and use beds and plant in the ground oh but buying some slow release organic fertilizer is good .If you decide on buying soil its okay won't hurt anything, but use organic liquid or solids fertilizing products. That you dilute in water .An use that only if your seedlings start showing signs of its hungry like yellowing .Once they get around a month start fertilizing regularly once or twice a week.