For ecommrece, it is best to use an existing Shoping cart, and not paying for a custom one, since it will be much harder to integrate it with other services/plugins.
For the easiest option go with a hosted shopping cart. Prices usually start at $20 a month and include everything you need to start selling on your own website.
Search for
3dcart
Magento Go
Shopify
Volusion
Big Commerece
And many more