The next person I see in a shirt with a dragon I am going to walk up to and just say -
"So...uh...really into dragons, huh?"
At what point is it acceptable to just have a dragon on your shirt? Even dungeons and dragons kids think that is nerdy.
Dragons are not bacon - you can't just add them to anything and make it better. This isn't Lord of the Rings, or Camelot or Hogwarts - and you aren't some knight in shining armor. You are a guy in his late twenties sitting at a bar trying to get a 22 year old girl drunk enough to come home with you.
Let's put it this way - if you were at the bar and saw a girl with a unicorn on her shirt - would you be impressed?