What kind of demos should be on my profile?

Your profile really only has three parts. The first is your detailed written advertisement. The second provides the actual evidence of your claims: your demos. The third is the ratings and reviews that you received when you completed a voice-over job.
 

Balance between written text and demos is recommended to keep the client interested. There is nothing wrong with having several demos. In fact, the more skills you can feature, the better.

The titles should clearly describe what the listener is about to hear. Remember, search engines can't read audio, they read words! The more detailed your titles and descriptions, the better.