There are others on here with much more auto experience than I so they may chime in.
Ina seems to have pointed you in a good direction. A quality aerated soil with at least enough food in it to get you through veg with just plain water would be nice. Fox Farms Ocean Forest is one of my favorite pre bagged soils but it starts out full of food so if you get it I would recommend to dilute it with perlite and worm castings, or with a bag of
Happy Frog.
If you are doing Coco and hydro nutrients then just start low and slowly raise up the EC. Less is more.
I have heard that 2-3gal for most auto's is generally a good sized pot. I wouldn't do any kind of training as far as topping or pruning because of their limited veg time. I have also heard they prefer to not be transplanted so it's a good idea to start them in their final container although I've seen some people transplant without problems.
I once ran this auto in a solo cup and it was a lot of fun! Way to small of a container. Just an example.
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