To really get enough traffic for building your email lists, a great source of traffic is the social media. There are many of them, but the most promising ones in terms of search engine optimization are Google+, Facebook, and Twitter. Learn how to create Facebook pages and advertise using the Facebook Ads.
Google+ too is equally great when it comes to generating instant traffic. It's only having a free Gmail account that is required. Twitter cannot be neglected because it guarantees traffic like Facebook, and Google+.