Build up a e-commerce website

Hi,

Depending of the needs...
You need to know whatr kind of product physical or digital product.
Shipping, payment, product options, the way the price will be calculated.
Localization, multisite, dropshipping, wholesale...

You may want to use a free and very complete solution, easy to edit with vqmod for custom needs.
There are a tons of module and template and the community is great.

Opencart
http://www.opencart.com/index.php?route=demonstration/demonstration

There are other solutions like Magento or Prestashop but their module cost more money and Magento maybe overkill for the needs.

Magento, OpenCart, PrestaShop,Shopify, virtuemart (Joomla),Woocomemerce(Wordpress) are thew most popular solution so you can check a few demo and see all the module and settings they have.