That tv show is gonna be a strange one considering how those books were written. Very much internal. I wonder how they will translate that on screen.
There isn't really any Evocation in that world. It's all Thaumaturgy or maybe even Evothaum. Some spells take a very small amount of time with very few components, and some are large and complex, but even the short ones can be miraculous. One girl turns a marble into a figurine and then brings it to life all in the span of a few minutes. Turns her fingers "impervious" (her words) for a short time in the process in order to work with the hot glass.
Everyone has a focus that they are better at than they are at other areas of magic, but it isn't a very limiting thing. You are still able to perform magicks outside of your focus, it's just the area of your focus comes more naturally than other areas.
The limiting factors in magic seem to be how smart you are and how well you grasp the "Circumstances," the atmosphere of magical factors around you, i.e. the closest ocean, the phase of the moon, the day of the month, etc. The Circumstances are a bit difficult to describe, but a strong grasp of them amounts to this amorphous awareness of the world around you and the magical energies within it that allows you to simply cast spells without needing to think too much about the Circumstances.
Magic is very rigid and very nebulous at the same time.
Not sure how much that helps.