I really would like to see more stories added to the group. Even if you don't need or want any feedback, the more stories, the more likely it will be that users will join. So I encourage everyone to add there stories in! Also, feel free to invite anyone to the group. I do want this to be a limited for now, but we only have a few members at the present moment.
Thanks to everyone for joining! I am having quite the experience figuring out how these work.

7410442
To be fair, adding stories doesn't really increase your chances of people joining the group. Yes, in theory they might notice that the story is a part of this particular group and decide to see what it's about, but the chance of them doing so is very slim. Most people really don't pay attention to that. Furthermore, regular members are unable to invite others--at least by merely clicking a button. Yes, they could contact others via PMs and comments, but that'd reek of spam. Also, it'd be better to specify what exactly you mean by limited, as the first two options you listed will lead to an uncontrolled influx of random members.

Your best chance at getting more members would be promoting the group in places that allow it, such as this group. To be honest, I wouldn't worry too much about controlling who joins the group. It's likely going to be just a couple dozen people, and more members might then just slowly trickle in. Nothing that'd make the group hard to police.

Thanks for the advice! I didn’t know invitations were only available to admins