As I've noted in the past, I dabble in many areas of geekery: tabletop games, video games, LEGO, Doctor Who, theater, etc. As a result, I also go to a nontrivial number of cons as my mood is stricken. Decades ago, I stumbled on a convention "fashion" idea that's worked for me, which may inspire you also.
I prefer, like many, to wear T shirts when I'm at a con (or, to be honest, when I'm living 98% of my daily life). But when I'm attend a convention, I try to wear a shirt that is not related to the convention that I'm at.
My logic is this: If I'm at (say) a Doctor Who convention, and I'm wearing a Doctor Who shirt, it's a conversational cul-de-sac: "Oh, I can tell by your shirt that you like Doctor Who. Me, too." There's nowhere for that to go, because it's self-evident by the convention you paid money to attend.
But if I'm at a Doctor Who convention and I'm wearing a Munchkin shirt? Well, suddenly I'll have folks go, "Munchkin?! Oh, wow! I love that game!" And then we strike up a conversation: what's your favorite set, some epic moment that springs to their mind, etc.
No, not everyone at every convention will get my unrelated shirt, but that's okay! It feels more special to discover fellow fans of Men Without Hats, escape rooms, Doctor Who, etc. in totally unexpected places.
-- Steven Marsh