It's open to interpretation, but the one thing which is most important for being a mentor is that you act nicely especially to new players. the worst mentors aren't the ones who aren't good at the game but the ones who are salty and rude all the time.

the Mentor system doesnt require you to be a good player for a simple reason, its not about that. it's about helping new players learn the game and as long as you have knowledge they don't, you can do that.