Before diving into a Drupal Commerce project, you must reconcile the product model and business rules of your merchant with the data model and processes of the framework. Thanks to its dependence on Drupal's entity system, Views, and Rules, Drupal Commerce is flexible enough to accommodate most requirements with little custom development required. However, to get the most out of the system, you must understand how it's using these systems and where it expects different types of data for products, transactions, etc. to reside.