In the end, though, you'll just have to take a chance with any FC. I'd say don't be too scared to join one, but yeah, I know it's really hard to tell which FC will be a good-natured one. I've met people and made in-game friends through doing things together from the Party Finder. Maybe one day you'll join a group of people through Party Finder and really like their company, so you could then ask to join a FC that one of them is in.