You should ask also in the Fig Forum.

I have found figs to be pretty tolerant of a wide range of potting soils. Because I need a lot (ultimately 25 gallon pots) I make my own using finer-ground bark (called "soil conditioner" in the garden centers of the big-box stores), a lirrle ground limestone, some baled peat "moss," and especially a significant amount of perlite to make it looser and lighter.

Poorly drained heavy soil is your enemy (root rot).

Using a complete fertilizer with all the trace elements (say, citrus or MiracleGrow) overcomes the very uneven nutrient content of the soil itself, which is made mainly for its physical attributes.