It depends on what you need and how much you want to pay.
Personally, I'm a great fan of Wordpress, but not for ecommerce. It was originally a blogging platform and you can now run very able websites via it's system, which in essence is a CMS - content management system.
Many hosts offer first class e-commerce solutions which are ready to go. You simply add your products and it's up and running.
But as I said, it depends upon what you need and how much you want to pay at the end of the day. Even with Wordpress, to get a fully function site, it won't be free. The plug-ins you need will almost certainly be chargeable.