Uhh...if I end up getting asked out by a guy, how do I let him know I'm a gay trans guy? Luckily I'm not really interesting in dating atm, but it's probably gonna happen since I'm in high school.
This is something to be brought up in an honest, candid way as soon as possible, but in a calm and private setting. Waiting until later just leads to hurt feelings, because the person you're with may be hurt that you didn't feel you could trust them. Just sit down with them and have a candid conversation about it. My best friend is a non-op gay transman, and he is now in a wonderful relationship with a cis guy who had never been with a transman before. My friend basically had to teach him about vaginas. But they're very happy! Honesty is the best policy. If you don't feel safe talking with someone about the reality of your gender and your body, you probably shouldn't be with them anyway.