You're gona have to setup a label for each category IMO.
I hate how gmail dont actually put the mail in to a folder, it links to the all mail, forcing you to archive.
I think if you just make a label for registrations (in the subject?), it will put those email in that label. Remember it doesnt physically move the email to the label, it only links to the original email, so I think you can have multiple 'links' in each label.
This is all speculation, so you're going to have to test it out.