CPA Traffic Dojo is traffic generation training by Christian Weselak that teaches the use of various ad networks. It focuses on less known and underused networks rather than Google, Facebook or the popular PPV networks.
There’s free traffic and paid traffic. Either has its advantages and disadvantages. To get free traffic, you have to put a lot of effort and spend tons of time doing SEO (or paying money for someone to do it), with paid traffic you don’t have the burden of SEO but you have to pay for PPC.