used monban and monban generators to

-create a user sign in
-create a user sign up
-create a user model

also played around with a couple of gems I wanted to test. they are not
implemented though here.
Signup/login don't work if there's no where to go. You aren't adding anything to the dashboard other than redirecting the user to it. Since it is already in your routes you should have it, or delete it from your routes if you really want it to be a separate feature and implement it later.