Google has their own site to help you learn how to use Google Apps, Learn Google Apps.

The site has tips on switching from other systems, tutorials, articles, tips and tricks, videos, examples of using Google Apps and much more. You can also learn by each app individually.

There’s even an weekly episode of the “Apps Show” where you can learn about new tips and features.

http://educationaltechnologyguy.blogspot.com/2015/02/googles-own-learn-google-apps-site.html?m=1