Just your username and a password.
Rankade is not a social network. The only people in your groups are people you actually play with, people you know and who know you.
In order to identify the user correctly, and to complete the sign-up procedure, you must provide a valid email address, as with any other online platform. Alternatively, you can sign up with Facebook or Google.
You can also create ghost users, i.e. users that are not linked to an email address.