You can always use a bagged soil. I have used Roots Organic many times in the past. Amend it for pests. Crab shell meal, Mosquito dunks, Neem meal, Nematodes if possible. These items will start killing any larvae. In my opinion, best to assume any soil is contaminated and start the microbes to kill 'em.
Search this forum for discussions about Barley Sprout Tea, Coconut Water and Aloe. Three excellent teas. Very cheap. I would collect local BIMs (Beneficial Indigenous Microorganisms) to start the soil off. Your local microbes are the best microbes. Why? Because through local natural selection they are best suited for your specific geographic area. They are the top dogs in your neighborhood. Put 'em to work!
After that initial inoculation, the soil will be up and running. Leave it be, or turn it occasionally if you want. I would avoid further teas, etc where the goal of that tea is to either feed the soil bacteria or add new "exotic" bacteria. As stated, your microbes have battled all others and holds the high ground. You're not going to buy better microbes.