IF you build it, they will come.
You can go a few routes here.
You can send private invites to those you already know and or trust.
You can post an OPEN invite and see who is interested then just host the party.
You will of course have to have the location for a gathering and know how many you will be able to fit comfortably in said location.
All in all it is rather EASY to have a gathering. The hard part is getting everyone on the same page to be able to attend on that given day.
I started the Hyenas Club for JUST such intentions. To get people together.
I held them in neutral locations.
MY first gathering brought only 4.
The second 8.
The third 12 or 13( a few no shows or it would have been 16)
The 4th, brought 19(there were supposed to be 60)which was the Chairity Event this past November 10th.
TTD