You could use an organic, it's hard to over fertilize with organics. Also if using soluble fertilizer, just use half suggested amount to be safe. A good one is Foliage Pro, it contains all trace elements. I always suggest trying different methods to see what works for you. Another fairly safe fertilizer is the time released Osmocote. I myself prefer dynamite, it last 9 months. I get mine online, postage free for a large bag of it.
This year I'm using Plant-Tone and the other Espoma organic products. I often use grains too like alfalfa, and cottonseed meal, makes it cheaper. When using organics add some compost to containers to make sure you have bacteria there to break things down.
Everybody probably has their own methods to fertilize. I just gave you mine that work for most plants, although each type of plant is unique. I'm fairly new to figs and I'm still experimenting myself. They seem like easy plants to take care of compared to many other fruit trees. I have peach, plum, pluot, tart and sweet cherry trees. These are difficult to manage, very difficult. Well worth it though!