General Ecommerce Advice
A is for Acquisition
In Google Analytics Acquisitions show you what's driving traffic to your website.
Organic Search - People clicking on your website in search engine search results
Referral - People clicking to your website from other websites
Direct - People directly entering your website address into their browser
Paid Search - From Pay Per Click advertising
Social - From sites like Facebook or Twitter
B is for Behaviour
Once a visitor lands on your site, what are they doing?
What pages are they viewing? How long are they staying on your website? Are they bouncing away to another site as soon as they land on your site?
Behaviour insights also contain data about whether your visitors trigger certain events such as playing a video, clicking a link or reading through content.
C is for Conversion
Did the visitor do what you wanted them to do? In the case of Ecommerce - did they buy from you!
Setup Goals in Analytics to track when users perform a certain action, and use Ecommerce Analytics to track sales. Without setting up Goals and/or Ecommerce Analytics you won't be able to tell if your marketing efforts are worthwhile.
Who needs a bunch of visitors if they're not buying anything from you?
The last word...
The ABCs above are the very basics of Analytics. Grasping these 3 cornerstones of visitor tracking and applying the principles to all of your analytics analysis will help you properly understand even the most complex of analytics tools.