Membership registration with Gravity Forms

ok, I know it's been asked before but I'm having trouble integrating this and could really use some help. As I figure out the specific steps I'll also post an overview tutorial because the previous posts don't seem to answer this questions in enough detail to create a definitive guide.

1) I'd like to use GF as the user registration form for Membership sign-up on my site.
2) Sales page/registration page offers membership details and when someone clicks on an option it takes them to the GF and passes along the membership variables like membership level of sign-up and pricing.
3) Prospective user enters in login creds and payment information and is then redirected back to the site (welcome page) after their payment has been processed.
4) Form adds them to the specific membership level after payment has been completed.

So far here are a few issues:
1) the test register page doesn't show subscription checkout options with [subscriptionform] unless I add them by hand (like at the bottom) [subscriptionbutton subscription="12"]
2) I'm still not sure how to pass along the specific variables in GF and link the form with the specific member level.
(currently have two hidden fields in the form registering the parameters: subscription and action)
And the form has confirmation variables that Pass Field Data Via Query String with settings: {Register Subscription:12}{Register User:20}
Current form url look like:

Problem: It doesn't work. ;[

I'm sure I'm missing a few pieces in here but wanted to begin the conversation and see how it all could be fixed. Any suggestions on steps to begin accomplishing this?