Hello, there are different platforms for which you could use some paid for free. The free would be woo-commerce works with wordpress now when I say free I mean that the software is free, you will of course need your domain name and hosting.
You can also use hosted solutions and like ecwid because (depending on the plan you use on ecwid), you can create a site on ecwid and if you use WordPress, you can add the ecwid plugin to your WordPress installation and your store can be found on your wordpress website plus they also give you the option to add your shop on facebook. So you create a store on the ecwid platform and you can place it on different websites.
I've used this wisely and I find that adding products to ecwid is pretty simple