You want to think about the value you can offer. You never want to address what they can do for you. It's the other way around. If you are adding value to your audience they'll be more inclined to evangelize for you. What you are talking about is really a lead gen campaign. I would suggest you create a lead magnet product and drive traffic to a landing page while trading that product for their email address. It's not that simple, really, but that's the base playbook. You can either purchase or earn that traffic, but most of the time I see people pay for the front-end funnel and make their money off the back-end.