okay, so i whipped up this demographic, and i was actually right - there's 5 main ones; male, female, agender, poly, and bigender, and the first 3 have one variation and bigender comes in 3 forms

i hope this is much better to understand than a long list of genders. it also clears up agender - i used to be confused whether it was seen as a mix of male and female or neither? but here it shows it as just a third one.
to explain the 3 main variations:
demi- is basically 'whenever you feel like it'. its kind of a blunt way to put it, but its for people who don't feel 100% attached to just m/f/a - the reason genderfluid isn't 'demi-agender' is because its similar to demi- genders and androgyny is part of it.
bigender is technically counted as one, like a compound - it's
one thing made of
two. however, it's the reason there's no trigender and instead it's just polygender. although bigender is a single gender on its own, you can't have 'male/agender/a-f bigender' grouped as one, because then it'd just be polygender. i hope that came out right?
yeah, if you have any questions, feel free to ask because im willing to actually passively explain this stuff to you instead of shouting snide stuff like tumblr sjws