How do you find a product that will make money through ads?

I have a business in the health food niche and sell a few products for around $6 – $15 but can't seem to make them profitable with ads. If I do a sale from ads (rarely) it costs more money to pay for the ads than the profit I'd make from the sale; resulting in a loss.

How can I go about sourcing a new product that would be profitable when using ads like Google, Bing Fb etc.?