I'm a current high school student. I (with the help of a moderator) just recently created a math club in my high school, and would like to ask for ideas about club activities. I was thinking of doing either combinatorics, graph theory, or number theory along with other kids. We decided that we are also going to do preparation for competitions, olympiads, etc. My school isn't exactly math-y so I'd like the activities to be fun and a learning experience as well. Any suggestions?