I have more than 200 plants in pots, and the best advice I can give you from more than 8 years of experience is that you’ll get the best growth by mimicking putting the plant into the ground (ie - placing it into the largest pot available). Use a wel draining soil, do not use any organic soil or products including soil that contains mulch. I use top pot from laguna nursery . Absolutely no organic debris in the soil as it will rot within 6-24 months and damage the roots. My avocados that have been slowly potted look scraggly nd have lots of dieback every season, overall slowing their growth. In the flip side, a 1 gallon avocado I placed in a 65 gallon fabric pot last spring is 5 x 5 ft in 11 months with beautiful lush growth that looks like my in ground tree (just smaller dimensions) without ever being burnt in the wind or suffering any dieback.
Just my two cents
Remember, nurseries are doing other things to their plants to maintain them in pots including root pruning, daily or even twice daily watering, fertigation, etc. with my pots, if I miss a day (and I miss a handful every now and then) and there happens to be bad weather. - too hot or windy usually— the potted plants will be set back quite a bit. Giving the plants headway early on is best I think, especially if you’ve got lots of experience with pots.
Khaled