Go with the 3 gallon pot first. One of the posts somewhere on this forum actually discussed why you shouldn't up pot too greatly at one time. I believe that doing so contributed to root rot.

A little constriction of the fig tree roots is said to promote early fruiting.

Root rot is nasty. Avoid it at all cost. I would go 3 gallon next spring. Then early spring of 2019, before dormancy break, check the root mass. If it is pot bound, then trim/tease/slit the circling roots. It may not be pot bound, which is unlikely, but do this next step in either case.

Plant in a ten gallon pot at this time, but only add soil enough to fill the pot to the 6-7 gallon mark, including the transplanted fig from the 3 gal. Pot. You are using a 10 gal. pot as a 6-7 gallon pot. The soil level of your fig in 2019 will be well below the pot rim by many inches. Always repot your fig with the soil line mark on the tree's trunk at the same place at soil level, no matter what size pot you use, or how low in the pot the fig sits.

In early spring 2020, lift out your fig tree, if it is aggressively growing roots, then fill the bottom of the 10 gal. with enough soil to raise the soil level to the normal height for a 10 gal. pot, a couple inches below the pot's rim with the trunk's soil level mark right on target.

In 2-3 years time, lift out your fig, and reduce both sides and bottom the root mass by 1/3 with a saw or sturdy serrated turkey carving knife, then repot with fresh soil. Do this every 2-3 years, ad infinitum.

Moses

Hi Moses

What is infinitum ?

Ad infinitum, is Latin. Translated, it means "through infinity." It's a figure of speech. In our case it means "repeat the same process, root pruning, and repotting every 2-3 years, as long as you are growing the fig tree."

Moses

Thanks Moses.