Visitors can only see one page

Hey! I got a website called I have built my site in different parts, on different subdomains with their own wordpress installation.
Now i am at my last site, which should be a site where only payed members can login. They will buy a membership at my store(, and I will manually register them!

When they are logged in they will find all my training tutorials etc, and also get access to my Team chat and so on.

But what I need help with is that I want to create a login page. Where ''No registered users'' can find links to where they can buy a membership. With some research I understand that i can not have widgets and so on at my default wordpress login page?

so basically, I want to create a site where no users just can see one page. Just a login page with some links and images, and the login field. Logged in users will see the "real" version of the site, with all training material and so on.. Do you understand?
My english isn't that well, but i'm trying to get better at express myself.

Thanks for the great support!