If you are looking to create a Shopify website and unsure of what to sell, a great starting point is to look to what is selling on Amazon. If a product is a top seller on Amazon, this already gives you an idea of what might be a good seller on your own website.
Having said said, there are other things to consider in selecting products to sell other than just raw sales numbers. You are going to want to look into competition, profitability, seasonality, total units sold on Amazon in a given month and a host of other factors, but certainly, knowing the overall sales of a given product is one of the main metrics or data points you will want to look at.
Some sellers are of the belief that you should only sell products from a category you are personally excited about, since personal excitement will translate into expertise in terms of pricing, marketing and other aspects of setting up and running your own eCommerce website.
Other sellers are of the opinion that your own personal interests are irrelevant to building a successful eCommerce business. There are obviously many successful businesses built around very boring products. Sometimes, boring products sell quite well, which is why reviewing actual eCommerce sales data is so important in selecting products to sell.
Whether your Shopify site is going to be a passion project about products you love, or purely a sales engine designed to give you supplemental income around best selling products, its always good to look at what are Amazon’s best selling products. This may not be an end point, but should certainly be a starting point.