Yes! Targeted traffic. Just increasing traffic won't get you registrations. You need to find the folks that will be interested in the service/site, and then work out a compelling way to get sign ups.
It sounds like you need to do this asap, in which case, I agree that PPC is a good route to take. It would be better to establish yourself as an authority, though, because people will see that you're legit and in turn, trust you. You will turn your cold leads into warm leads by establishing that trust.
If you can do that on your landing page somehow (guarantee, testimonials, proof of results, etc.), your conversions will improve.