login with social and erase gravatar

good morning

topic login: I do not like Gravatar and I am sure that in Italy forcing users to further registration can only lead to losing users and customers.

If then a user has the ability to register only with email (now too simple), the risk is to have a user who registers with more email .. so not unique.

I would not like to activate a registration system linked to user verification with a phone number.

I think, I do not know if I’m wrong, which is better to allow registration on my site through the social networks to which you have already registered … eliminating gravatar and keep a chance of normal Avatar?

how do I delete Gravatar? do you have a video or explanation about registration via Facebook, Google+ etc ..?

Thank’s