You have to abide to the rules of the instance in which the community/magazine is. Any extra rules in the community are up to you. And yes most communities are are ghost towns especially if they are about something more niche or with a smaller audience. Usually the way to grow them is to create content to attract new users, nobody wants to join an empty community after all. You could also try to advertise it on !newcommunities or something similar to gather some attention. I hope my answer was helpful, that’s just my experience, I’d be interesting to hear others’.