Parse, firebase, pubnub and others work with Phonegap. You don't need a plugin. Just use the Javascript framework each provides. Or use the REST API. They all provide some type of REST (althought pubnub is not well documented.)
I know firebase has a scoreboard example app. I'm pretty sure Parse has one as well. Sorry I don't have an App for them that I can share at this moment.
As for facebook tutorials, I don't do facebook. These blogs are your best bet:
https://iphonedevlog.wordpress.com/ (Steve Husting - blogger)
http://simonmacdonald.blogspot.com/ (Simon Macdonald - Phonegap Contributor)
http://www.raymondcamden.com/ (Raymond Camden - Adobe)
If you have more questions, please ask.
Jesse