I'm going to say something rather controversial, but considering I'm a black bisexual man, I feel I can say it without too much back lash.
Fuck diversity.
Don't create characters for the purpose off checking of diversity check lists. Don't feel obligated to add characters into your story just because a specific group isn't represented yet.
With that in mind-
Don't make "gay characters" make characters that are gay. Did you catch the difference? Don't make "black characters" make characters that are black. I did it again, did you catch it?
A person's race, sexuality, or religion isn't all that they are, so don't create those. Create characters that have those diverse traits. Stay away from stereo types, but don't go too far into the opposite direction either. A person race will affect their life mindset and ideas. The same can be said about their sexuality and religion. Understanding how the traits your giving people would actually behave in a real setting can help you understand how to write them into a character.
But don't be heavy handed about it either, because that's even worse. You should never have to outright say a gay character is gay. You shouldn't have to make them dress a certain way either. Be creative. Let the reader know the character is gay through his actions or ideas.
If a person is Trans, for the love of God don't call them a gender neutral or something like that. Instead, explain the way they dress, their hair, mannerisms, and voice. That way, the reader can imagine a gender neutral person rather than having to awkwardly read that's what they are.
What sounds better? Choice A:
"Dakota wore attire that didn't cling. Their hair was short, but their skin was so smooth. I couldn't tell if I was speaking with a boy or a girl. I was afraid to ask, so I avoided the question."
Or Choice B:
Dakota was a Trans woman.
You'll notice that while one might take a little more effort, it's definitely a lot less abrasive or stark. Choice A is more detailed and also avoids using any strict labels.
If your writing a black character.... he doesn't have to have an afro. His skin doesn't have to be night sky dark black. He doesn't have to speak in ebonics. But understand that different races have different experiences. Even a black republican has to admit, because of their race, they have to say or do specific things to .........
I'm beginning to rant here. I just got off work and this particular subject has so many layers to it I could probably write a thousand page book about it. If someone else can pick up my wavelength and continue my train of thought, I'd appreciate it.
But for now
Don't worry about diversity, but if you make a specific type of character, make them more than that one trait, and don't be heavy handed about letting the reader know they have that trait. Be creative and try to be nuanced.