Post donation we call dataLayer.push({'event': 'Donation', 'conversionValue': donationAmount}); where donationAmount would be the decimal amount of the donation.
On registration, we call one of the following:
dataLayer.push({'event': 'Registration', 'type': 'Quick'});
dataLayer.push({'event': 'Registration', 'type': 'Post Donation'});
dataLayer.push({'event': 'Registration', 'type': 'Detailed'});
dataLayer.push({'event': 'Registration', 'type': 'Step - ' + stepNumber}); where stepNumber would be the step they are completing as part of the detailed 4 step registraiton.

 

https://support.google.com/tagmanager/answer/6106716?hl=en