I'm gay, and my main character is gay.
Before I get into tropes, I wanna say I've actually have a lot of back-and-forth with how I view it. For instance, some people say they hate when gays are portrayed in negative ways. If you've seen The Mist tv show, the main gay character does some pretty bad things, and it's in relation to his gayness. While others say they hate how gays are "safe" from negative plots.
I get both angles. Homosexual representation in media is a pretty new thing. So I get the need to make sure that we represent them in positive light. We don't need gays to be portrayed more negatively, because they already are. At the same time, they are equal to straights, and are equally able to do negative things.
Thus, I'll say this: I think homosexual characters should be open to anything, from being the saving hero, to being the horrible villain. However, their villainy shouldn't be related to their homosexuality in unrealistic ways. For instance, in the Mist tv show, the gay character rapes his female best friend, because he doesn't have any love, and doesn't want to be alone. Everyone treats him poorly for being weird and gothic. Granted, the show was canceled, and it's possible the direct they would had taken was that bullying can lead to mentally disturbed individuals, which is a better route. Yet, it comes off like being abused leads to being gay, which is... sigh.
As for tropes. I don't read books that are gay-themed, because I read books for plot, and not for social issues. So I'm probably not the best gay to ask about tropes. That said, from what I've seen, I also hate when gay characters don't get any kind of happy ending. That said, I don't usually like stories where it's entirely a negative ending regardless. Bitter sweet is more powerful.
I don't like it when being gay is their identifier. I deal with this in life, too, which I simply laugh off. However, if I'm introduced to a group of friends, or new to a workplace, somehow, me being gay is brought up. Who cares? No one brings up when someone is straight. In the same vain that it's annoying to read, "Cathy was pretty and bright," it's annoying to read that a character's identifier is that they're gay.
In my fantasy action adventure book, my MC is gay, but you don't even "know" that until the very last page, when he kisses a guy. I kinda did it for two reasons. One, I wanted my book to be marketable to people. I wanted (straight guys mainly) to be able to read the whole book, see how awesome the MC is, and how crazy the plot is. Fall in love with it. Relate to the what seems like intense friendship between these two guys. And then at the very end realize he's gay, and think to themselves, "Yeah, but he's awesome." I wanted its subtleties to allow the reader not be threatened by his gayness, and slowly become open to it at the end. However, not all books need to be that way. It just doesn't need to define them.
I don't find the christian thing to be a trope. Happened to me, and to most gays that struggled. Hell, I felt Prayers for Bobby really hit home what it can feel like for both the child and parents of a homosexual.
I also don't mind the falling for gay best friend thing. That's super common haha.
Above all--while I didn't do this in my book, because of its nature--I wish humor and gay were intertwined:
Humor normalizes concepts. When I came out gay to my christian parents, it went as one can imagine. However, I inserted humor throughout that summer. I was clever in doing it. When something gay happened on tv, I'd make a joke. When someone said something, I'd sometimes make a gay joke out of it. At first they were confused--I made a joke about myself being gay? Then they'd start to chuckle. Then laugh. Then they'd start to feel comfortable making jokes themselves. Then me became so normalized for them, that my mother started telling me to date certain boys she found sweet haha! My point is that humor is a normal human trait, and being gay shouldn't be this constant serious thing. If it is, it continues to separate the concepts, allowing people to stay at arms length.
A good example of this is Easy A. While it's a comedy and had many times to make jokes with with gay character (he was always involved, and not the brunt of the joke; that's important), it still serves as a good example. The interaction between Olive and Brandon is a true representation of my interactions with real people. Just how we have serious conversations about me being gay, we also have a lot of humor around it.
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Thus, to summarize: make your gay character real. Don't make them immortal to making bad choices. Don't make them immune to criticism and jokes. Making them real, makes them relatable. Making them relatable makes people who normally never be around someone gay, begin to see how human we actually are.