As this Sound, you already Know the Difference between the Paid Marketing.
Joining and Posting to Facebook groups, Joining and Posting to Forums like Nairaland and other Related Forums, Sharing your content to social media platforms like twitter profile, Linkedin, Instagram feeds, Tumblr Feed, Google+, Building list of email Subscribers and Mailing them using some plugin and Marketing Companies like Mailchimps, Autoresponders, Aweber, Mailpeot Plugin for WordPress, Jetpack email Subscriber Plugin for WordPress etc
As this Sound, you already Know the Difference between the Free Marketing.
Facebook Sponsored and Boosted Content, Nairaland Targeted Ad, Twitter Ad, Email/Bulksms/Phone Number Database, Forums Featured Contents and the Like.
The Summary…..Both the Free and Paid Works Well, but the Difference is not How you use them, but what you archive using them.