The efficiency of Facebook Ads depends on so many different factors, that you need to examine a variety of different things in order to understand the reasons why a campaign might be underperforming.
First off, it can be your targeting (the people who are viewing your ads might not be interested in your product). Then it can be anything from the visual (might not seem appealing/interesting), the copy (might not be engaging or providing information), the budget ($3/day for your targeted audience might be too little), a combination of the above, or a number of other unrelated issues.
What I'd suggest is taking a good look at the above and restructure your funnel. If you're starting now and your site has no or few visitors, then it's oftentimes hard to identify your potential customers immediately. What is a good strategy for these kinds of situations is starting by targeting a broader, interest-based audience with a low-cost conversion strategy (such as Traffic). This will become the top of your funnel. Then proceed by creating lookalike audiences from the people who actually visited and targeting them for purchases. Lastly retarget people who have visited but didn't convert, since these are the ones who are closer to a sale (your bottom part of the funnel).
Online advertising for e-commerce can seem easy and daunting at the same time; the overall idea though, most of the times, remains the same.
Thank you for your detailed review. The problem was that my campaign was directed at only people that liked my site. Since there were none, hence the problem. I've created a different target audience and now there are click and signs of life. Thanks will follow your advice.
An intentionaly crafted sales funnel is about 100 times more effective than a sales funnel which is left to random chance.
Optimizing your sales funnel is absolutely vital if you want to make more sales, convert more prospects, and build a more successful business (which, of course, you do). I'd recommend you also check out this free training if you'd like to know more about how to set up high converting sales funnel.