how can you get into social circles?

Guilds aren't always just for the name. In my opinion, guild can be a better buddy list than the buddy list itself, because you have this group and everyone in the group can hear what everyone else is saying; no one's left out or confused by hearing only half a conversation. However, it's best when you already know at least a couple of people from the guild, because then you won't feel as much of a stranger, but you'll also be able to meet new people as well.

This. So much this. My guild has existed for a year, and started out as a small circle of friends. I knew around 3 of them, and joined in around month 3 to help with GPQ. And we've been tight friends ever since. We've all been there for each other, had fun, joked around a lot, killed a few things, met lots of new people, and seen a few good friends leave. But the family never dies, and we'll keep it going for as long as it's possible.