Pot size depends on the size of plant. I wouldn't go to big at first. Then adjust it each year by increasing maybe 2" or so in pot diameter based on growth. You could use a well drained premade potting mix for cactus/citrus/etc or make your own 5:1:1 mix that is really popular for figs. It contains 5 parts pine bark fines, 1 part peat moss, and 1 part course perlite. I'm new to figs too so take my comments with a grain of salt. There are some experts here that can make better suggestions.

Susan it depends on the size of plant you bought to determine the size of pot
it may need , as a general rule they can grow fast outgrowing their container.

Keep it simple for now .
Since its your very first fig tree i would go with store bought potting mix , for years i used simple miracle grow potting mix with good results.

Eventually tried all sorts of different brands including making my own which can be time consuming
and back breaking depending on amount of plants and pot size so now these days i just use pro-mix brand.

Keep it simple just starting off and enjoy .
Martin

Thank you so much. The fig is in a small pot. Maybe 4 x 4 and 6" high. The tree is about two feet tall. I got it at a Rutgers plant sale this past weekend. It's Big Al's Black Fig. I thought miracle grow might be too heavy, should I use their regular potting soil or cactus mix? I also have a bale of pro soil (maybe bm1??) that I use for starting my seeds. Is that better? Thanks for the advice.

Hi Susan6, welcome to fig growing and this forum. If your plant is already two feet tall, I would up pot it to a two or three gallon container. If it has a good root mass, MG potting mix amended with perlite should be fine. Too small of a pot will be constantly blown over by the wind and figs have a tendency to grow rather quickly. You may have to repot again depending on the growth. Don't forget to gradually introduce your tree to the sun, this will prevent sunburn. Good luck.

Ok, I will repot it tomorrow and keep my fingers crossed