There are three things to pay attention to. The first is to use specific keywords to the product being sold. You don't sell a shoe. You sell a jogging shoe. Even more specific, it's a woman's jogging shoe. Too many simply bid on shoes, get their ads shown thousands of times, get a handful of clicks and no sales. The second is to have an exciting ad. Just saying that you have shoes (even if you say you have women's jogging shoes), is boring. You need to get the searcher's attention and give them a reason to click. Third, your landing page has to convince them to buy from you. Close the sale. Your ad got them there, finish the job. If your sales message is no good, you won't sell.
Too many advertisers use irrelevant keywords or too generic (like shoes), quickly put together a poor generic ad that gets few clicks. If you want to sell your products, you got to put the proper effort into it. Create an ad group for each product using targeted keywords, a great ad that promises to fix their problem and land them on the page for that product, not your home page and make them search for what they just searched in Google. With a landing page that gets them excited buying from you, you'll be successful and profitable.