I don't understand this. Maybe you have misunderstood what you need to do on Gravatar.
When you apply to join Gravatar it doesn't ask you for any 'required information'. You simply set up an account by providing an email address (which for it to work on AB needs to be the same address as you use for AB) and a password of your choice. You then attach an avatar.
Of course if you later want to return to the Gravatar site you will need to remember your Gravatar log in details. If you can't remember them you'll need to set up a new gravatar account.
If you need to us e anew email address for Gravatar you'll also need to change your email address on AB. you can do this via Edit My Profile
Maybe you should try again to set up a Gravatar account
If you still have problems, come back on here and let us know at what point the process fails and what message you get, and we'll try to help