I have a very small social circle, and I feel like it's time to expand it.

I lightly keep in touch with some guys from college (we were cool there but didn't hang out outside of it), we check in on each other about once a month or every few months. Each one of them has huge social circles that expand very far.

I was once invited to join one of them and I feel like we both had a blast.

Thing is, when I say that we should do something or meet up (in a general sense), it usually amounts to nothing. And I don't have much of a group to invite them to do stuff. I'm not sure if it's backwards or whatever but I prefer to be tagged along to their groups, as opposed to inviting them over to do stuff.

Am I looking at this wrong? Can I get myself invited to their night outs? If so, does anyone happen to have tips?

Thanks ahead!