what ev said. if youre set on having a lot of lgbt characters in your stories, you could have the characters happen to know each other from a pride parade or some other sort of lgbt community. or, perhaps you could set it in a time period where that stuff was considered normal. for example, in ancient greece it was fairly common and wasnt considered any sort of social identifier, though that was mainly between 30something men and pubescent kids. you could either find one of those times or come up with a world similar to our own but different in their views on sexuality. or, you could write a race up where thats the standard. for example, all elves are bisexual if i remember correctly. you could write about an elf society or something with similar customs and "norms" if youre set on having a ton of lgbt characters.
if youre trying to stick to our world, though, id say a good rule of thumb is to only have maybe two or three, four if you want. try not to have everyone be gay, but try not to only have that one gay character. as they say, the only thing worse than no black friends is one black friend. avoid token characters as much as possible, for example dont write in a straight character just so you can have more straight characters. if youre in an area with a higher lgbt population, say los angeles for example, youll have a higher count of them, but its not as likely to be found or at least outwardly expressed if youre down in the bible belt. if youre in new york, youll have a lot more hispanics and black folks than youll have in other areas of new england like the aforementioned vermont. if youre in the bible belt youll have a lot more christians than atheists and in the midwest youll have a lot more germans than brits. some areas are more of melting pots with a little bit of everything and some are more homogynous. i could go on. just try and figure out where exactly this story is set in (nothing too specific, just "small town in ohio" or "on the ocean off the coast of portugal" and stuff like that) and then look into the culture and diversity-based stuff from there. just make the diversity appropriate to your worldbuilding. you wouldnt have many high-standing black people in a story set in the 1800s and you wouldnt have a million outwardly gay people in the bible belt.