If you go to Special:Gather or Special:GatherLists when you're not logged in, you're presented with a login form. The form has no context to explain why it is showing. This is a missed opportunity.
- Show a page that explains you can only start making collections if you log in or sign up, with links to the login and sign up forms (I like this one best, myself)
- Put a message on the login form explaining why you have to log in to use Gather