Marketing?

​               Being a self-published author has its challenges. One of them I find particularly taxing is the marketing of my book. There are so many confusing voices on the Internet telling me that if I purchase their service, my advertising will reach hundreds (or thousands) of people. How do I know what is true – what works and what doesn’t?
               Of course, there are many ways to market my book without spending money, such as approaching bookstores, libraries, joining groups on social media, and sending queries to podcasts and radio stations to interview me regarding the book. It’s the advertisements that promise me the moon that I’m unsure whether to invest in or not.
               For example, I purchased an ad on one of the social media sites and ran it for seven days. I got clicks but not purchases. I gave up after one campaign. But should I have? I receive blogs regarding book marketing and one blogger stated that you have to keep trying different ads to see which ones are successful and which ones are not. This makes sense but it also costs money.
               I think my quandary is where will my advertising dollar have the most success? And when you get right down to it, the only way to find out is by trial and error. Not very reassuring. But I’ll keep plugging away. Giving up is not an option.