Your profile is the first thing that represents you in the chat and on the site. A profile with no avatar and no description is like standing in a crowd with your back turned: nobody thinks anything bad of you, but nobody comes closer either.
All of the profile information is optional. You can chat without filling in any of it. But an avatar and a line or two of description visibly change how quickly people get to know you.
What to share and what not to
Your city, your interests, the music you like — these are the details that start conversations. Don't share your full address, your phone number, your workplace or the name of your school. Your profile is public; a detail that looks harmless today may not be harmless tomorrow once it is combined with another piece of information.