Without paid advertising, how do you advertise the service? I've created a micro-service like this in the past, and where I really fell short was getting the right people on the site. AdWord conversions were also too low in my case.
I worked hard to get onto the front page of google for "email to google drive", and I have a few links from other places that drive a bit of traffic.
I experimented with adwords and stumbleupon but nothing caused enough conversions to be worth it. Every now and then I turn adwords back on to play with keywords a bit, but it's just not worth it at the low price point.
