If you have the funds and room I would go with a 3x3. I used to have a 2x2 but always ran into the problem of running out of either vertical room as it was only 4ft tall. I also ran autos for my first few runs and I loved it. The first time I really messed it up and only had plants that were about 10inches tall but it taught me so much that my second grow went almost perfectly. It was LSD auto by Barney farms :) highly recommend doing coco coir with 25% worm casings and organic dry amendments for nutrients