Is gendefluid only between 2 genders, like male and female or male and agender, or can it be between three different genders?
As far as I'm aware, genderfluidity doesn't have a limit on the number of genders. One could be male-female-agender-nonbinary genderfluid, for example. (Most genderfluid people I know or know of fluctuate female/male/nonbinary or female/male/agender, so three is far from out of the question, haha.)
Genderfluid means a person shifts between the different genders. Could be 2, 3, 4, etc. I know I shift between 4-5 but there are some who shift between them all.
I don't think that there is a limit either. If you want to spicy though, there are terms like pangender and trigender, but that's something that is up to you to decide