Question How to make a certain rank make factions?

I'm beginning a public server soon and I'm trying to use a new and unique way of managing a factions server. I want to make it so only certain ranks can actually make factions, but normal players cannot. I'm also looking for how to make it so any player can join any faction at any time. Basically it will be something like a few major factions where each faction will compete to try to have the most members, and they will do so by persuading players to join their faction. I've never set up a server before and this is my first time making a permissions file, so I'm kinda lost.

Basically the main problem is that I can't get normal players to be able to freely join other factions without an invitation. Is there any way I could make this work? I just can't seem to find a way by myself.