Do you want to be organic, mushroom? If you are OK with anorganic fertilizers, I find stock and cheap MiracleGro works very good. It's supposed to be quite pure and it has not only the "big three" nutrients (N-P-K), but also many micronutrients.
Also, the same company, Scott's, has a slow releasing fertilizer in pellets, called "Osmocote". These you can use if you don't want to apply fertilizer that often. I've never tried it, though. I like to "hand fertilize" whenever I get the feeling the plants are hungry.
If you don't overdo it, your soil will do fine.
If you go the organic way, then, besides the usual "building blocks" (manure, bone, blood, compost), there are also organic MiracleGro style fertilizers. You apply them in the same manner, and don't have to worry about "building a balanced nutrient mix". However these are quite expensive and not vegan (the reasons why I don't use them and stick with "chemicals").
Also, a soil test can be a good thing, if you intend to build up your soil. The testing company will not only tell you what is and is not in your soil, but also give suggestions for what to add. Some companies even give "organic" instructions, if you indicate that you're an organic gardener.
I've never done that though, because I've never owned a garden that I knew I will cultivate for years and so never wanted to build a rich soil. So far, I've always gone the quick fix MiracleGro way.