It's impossible to be a Gnostic in today's day and age. Like even the Amish people have more property and stuff than a Gnostic would be allowed to have. I guess one could be pseudo-Gnostic. But that's not any better than being a pseudo-Christian. What I'm saying is, nobody goes around identifying as a Gnostic. They just call themselves Christians. And there is clearly no point in trying to argue who the real Christians are.
The real important question though. Is do you want to be a vampire hunter or not? If not, than don't worry about what's real or what's true. Go be food to some psychic vampire. Because trust me, there's millions of them out there. Pretending to be Christian and Muslim alike. They feed off of negativity, like a demon I guess. But they aren't possessed by demons. Well maybe they are, but they seem like people to me. People who feed off emotions like a vampire!
When it comes to gender, I think of it as nothing more than what Jung would call a complex. So a complex could come to personify any number of genders, creatures, or even objects. Like steel. Let's say I have a steel complex, in that. I believe my body is actually made out of steel. Never mind that I can't punch through a windshield like the Terminator. I still think I'm made of steel! And I highly doubt anyone would classify that as a mental illness.