Since Firestarter GUI needs Admin rights to start, does it make sense to autostart firestarter on boot and how can i do it?
You can't start a GUI app on boot because it needs to be attached to a graphical session, the graphical session is only setup after you login. You could set it up to start when you login:
System -> Preferences -> Start applications
Add whatever command is required to start it, if it needs admin privilegs you may need to change your /etc/sudoers configuration so that you can start the app with admin privileges without asking for the password.
Update1: You can check how to edit the sudoers configuration at: https://help.ubuntu.com/community/Sudoers There is an example there on how to allow to use the shutdown command without a password.
With the following steps firestarter can be autostarted