Dear Claire:
If I was you, and if I wanted to get to know the guy better, then I would make the first move, messaging the guy that I find him appealing and would like to get to know him better. Then I will wait for his move, if there is none, it is done. If there is a reply, I will evaluate the reply. If the reply will be about getting together for a casual encounter, I would reject his move because my goal would be to get to know him better, not to have a casual encounter.
If on the other hand he responds with a suggestion to communicate online and/ or in person for the purpose of getting to know each other, then I would proceed and communicate, take it slow, get to know each other and decide later if you a relationship is a good idea or not.
anita