As per Facebook API v2.0, /{user}/friends
will only return friends who already use your application.
friends
endpoint will only return id
and name
(in v1.0 it also returned installed
field, but not anymore as it's now restricted to app users only).
If still useful for you, you can get friends gender by calling /{user}
on friend's IDs.
Cheers!
Edit: Removed user_birthday reference