1. If a group doesn't accept your request for a day, you consider that they don't want you or they aren't so active so stay away.

2. If you aren't in any group, start one of your one and then leave.
More simple

3. The game gives you some suggestions (mostly from groups of your friends or from your country)
You can also find some groups from here, from Associations section.
There you can talk also.
And there are some fb groups where you can look for an asso.