IMHO
sessions, singarounds, and Festivals would be the best places if you want a shared interest in Folk.
If you are fit, ceilidhs are a great place to just enjoy the social atmosphere. Whatever else transpires is a bonus.
If you lived in Gloucestershire UK, I would recommend Stroud Ceilidhs. We have a policy of not having morris or song spots, in the break, so that people can mingle, socialise and re-fill their glasses without missing-out on any given dance. And the committee and a few regulars make a point of asking wallflowers to dance, and reminding them that any woman can ask a man and no-one will think it at all strange. And the latter is pretty much de riguer in most ceilidh series I know about.
Stroud Ceilidhs the first dance of the season is on (unusually) a Friday and part of the Stroud Folk Festival 26th - 28th Sept.