I apologize for the late reply, I hope you may still find this post useful.
I'm currently using Pidgin and Jabber, so far it has worked out very well! File transfers are quite slow, however video and audio chatting works, although you do need to enable it: http://michael.stapelberg.de/Artikel/video_chat_with_pidgin/ However, you might not need to install any packages on your computer, try enabling the "Configure audio/video" plugin first (Tools > Plugins) to see if it works.
Any one of the servers on this list will do as long as it supports Multi-User Chat: http://www.jabberes.org/servers/ Or you can use Jitsi's Jabber servers with Pidgin, however in chat rooms, you cannot initiate group file transfers, audio, or video calls. File transfers do run quite slow (about 10KB/s), however if you're patient, you can transfer a small 5MB file in about 5 minutes.
I wouldn't suggest using Jitsi as a Jabber client even though others have suggested using it because it runs under Java, and I have a few friends (one of which I used to go to school with) who have reported it slows down their computers. Pidgin, on the other hand, runs natively so it doesn't slow you down as much, and it also comes preinstalled on Trisquel, and it also has a Windows version available for your friends who don't use the GNU Operating System.
Last year in November marked one year since I stopped using Skype and deleted my account in 2013, and I have not once felt the urge to reinstall it on my computer. A few of the people on my contacts list at first hesitated to switch to Jabber with me, however once they switched over, they actually liked it!
