I agree with what everyone's said so far; you should be able to cosplay what you want.
I want to add something about the roleplay part someone mentioned on Homestuck. Most fandoms tend to have really outgoing people that like to make all sorts of series references and in-jokes (which is great, I love that kind of stuff). But I do recommend looking up or asking a friend about popular memes/jokes if you're the kind that doesn't like feeling out of the loop. I know I would feel really awkward if, say, they're all making some sort of joke about how so-and-so character "gets around" and it happens to be the character you're cosplaying and you're just have this clueless smile on your face like
That being said, if you have no problem or think it's still super-enjoyable then do what you want! :3 I just know that personally I'd at least look up a few in-jokes so I wouldn't accidentally become the butt of a joke or something without knowing it myself.