I live in fig country - no need to plant them as theey groww wild everywhere. I have 'tamed' a few though. Figs need very little fertilizer. If you fertilize more than twice a year, its too much. Pot size doesn't matter. I had one (until recently) in a 2 gallon pot for about 15 years. Never repotted and never fertilized. I barely took care of it (care was adrpper to its pot) and it thrived. They do better with regular water but keep them on the dryer side of wet.
