Just looking for basic Auto advice, or...?
For Autos it's best to feed on the light side until you determine that strains needs, and you should start in the final pot. Transplanting can be a stress on the plant and may set back growth, best to avoid. The trick then is not over/under watering in the early days as the plant builds it's root system. I like to give a cup or two (depending on pot size) every few days, poured in a ring midway between the seedling and the pot walls.
For training I use a lot of LST (low stress training) like bending the plant over horizontal after 3-4 nodes (sets of branches), making for many tops
. You can see I split the main stem, but no worries, she'll be fine
I'm no expert, but if my Auto experience can help at all I'm happy to share, I've learned so much here I'll never be able to pay it all back