Am [well, at least currently] a CMO - reach out if you want a basic intro in marketing stuff, looking at forming it into some sort of guide/course to sell, but ping me a list of questions and will try and pass on some tips and links to get you cracking.
But as others have said, if you're wanting to gain traction for something, it doesn't start with "cool project" it starts with "solves a problem". Cool is great, and amazing and the personal satisfaction is priceless - but if you want to price it, it's a different approach.
Of course you can market something without physical cash investment, the flipside is then obviously a time investment.
All advertising is a form of marketing, but not all marketing is advertising. Marketing tactics usually fit on an axis between cash-poor/time-rich and cash-rich/time-poor. Pick which on you can optimise for.
Take a look at "Inbound Marketing[0]", it's a good book that shows you how to gain an audience using social networking tools such as Youtube, Facebook, Twitter etc. It's an old book in terms of how fast social media moves, but it's logic still applies.
Well if you can't afford to purchase some books on the subject (which are helpful in their own rights), then I would suggest spending time looking at Blogs that specialise in the subject and check out Reddit's marketing and entrepreneur subreddits. They are really helpful and you can ask what ever questions you need.
But as others have said, if you're wanting to gain traction for something, it doesn't start with "cool project" it starts with "solves a problem". Cool is great, and amazing and the personal satisfaction is priceless - but if you want to price it, it's a different approach.