You have two that agree so there is a start. The question comes down to how much time do you have? How much space, access or willingness to look for natural ingredients. If you have a yard or neighbors and with one then you have a good start, access to fresh manures is certainly a plus.
Call me old school or cheap I buy very little from the store for my mix, but I am retired now and I have always had a farm so composting as woodashes where always a plenty. I start with native soil, the best I can find in a close area to where you live. I build the rest of the mix around what I round up. Composting can be done in a small space depending on your needs and whether it will be a small or large part of your final mixture. I keep 3 going, a fresh one which gets all of the yard waste, banana trimmings, bird of paradise and basically everything else that is cutdown. I gather manures from pastures, roads (I live where they still move cattle up and down the roads to change pastures), anywhere I can find them.
The second pile gets which is now finished and gets all the kitchen scraps, coffee grounds, egg shells and rotten fruit and I empty all the containers after harvest to this pile and turnover monthly. This usually sits like this for about a year.
The third pile is the one I use to fill my containers.
Good luck in your search