I get this question from artists all the time. Is there a such thing as effective free promotion? The answer is yes and people use vine, youtube and other social media outlets to get free promotion all the time. The main thing is the people that get tons of free promotion are committed to delivering high quality content daily. This means they went out and purchased cameras, lighting and mics so they can deliver. You have to work extremely hard for free promotion. Its much easier to pay but if you don't have the money the work triples.
So if your not willing to put out quality content daily or at least 3 times a week then pay for marketing.
Content>>>>Marketing>>>>Feedback is the only way to run a successful business.