Can't get Varnish working properly, not caching anything. (varnishd is running , status is tick)
By default, Varnish is not working on port 80 (and in this case it could not be either since your Apache is occupying that port). You should configure your Apache to listen to another port, then use that port for your backend setup in Varnish. You should also configure Varnish to listen to port 80.

To debug, you should try to figure out what port your Varnish is listening to now and browse using that port, then you should see traffic in varnishtop.

The reason I'm being vague on the varnish configuration is that I have only used Varnish on CentOS which reads in the startup defaults from /etc/sysconfig/varnish - since you are using Ubuntu you should try to find out where that default configuration is being kept on your system. A fair starting point might be the /etc/init.d/varnishd script which might give some clues.