Organic is all about locally sourced soil. Those are the microbes that flourish in your environment. They will also use materials from around you, that react with the local water supply right. If it needs soil sweeteners, the manufacturer will have already have added them. This means you need to use the local water, no bottled water or RO water. My recommendation is Kellogg's potting and raised bed mix. A local nursery is a great place to look also. Say you are growing roses, or nightshade family plants. Those are peppers, tomatoes, etc. These plants have the same nutritional needs, and water/drainage needs.
If you do not demand an organic soil, Proven Winners. They make the greatest soil for growing amazing flowers. Their soils are sent around the world to top notch horticulturist for input and development.
Kellogg's and Proven Winners is available at big box stores like, HomeDepot and such.