Organically grown traffic will always outperform paid traffic if done properly. Using an informative squeeze page that not only lets the viewer know what you offer but also a hint of what you expect will help filter your free traffic and help “weed out” those that are not truly “targeted traffic”. Unlike paid traffic, a targeted traffic is always the best option–simply put–give them a reason to hang around after you have grabbed their interest!
As far as the unwelcome emails- Use a res-ponder with stats as to who has opened and interacted with your email (I use Mailchimp). This way you can control your list and know you are sending to an individual who “wants” to interact with you.