Hey friend,
This is an extensive topic to discuss on a grow question.
I would do a little research to see what starting point interests you the most. There are soil blends out there that are a great way to get into growing without headache. I have seem amazing results from fox farm products, when I grow in soil, I will start there.
Premixed soil blends can yeild results with very little additive, if any.
Realistically, it is not that hard to make your own organic mix, you just have to look up what cannabis plants like.
Your local gardening store should have everything you need to get you started.
Hope this was useful,