Your mail will be grouped by circle as well

You google plus circle after manage it well, it will be automatic re-used in your gmail mails, so that you can see which mail come from who by your managed circle. It's amazing!

Who to follow unofficial recommendation

Share with you what I found so interesting categories that you might find them useful to follow

http://www.recommendedusers.com/

But we can't find Cambodian people over there, do you have some list/circle to recommended from Cambodia? Share together and build our network on Google Plus

Basic Usages for Google Plus but important

Google Plus Features

Manage Your Circles, Put people in right contact/sharing

Knowing how your streaming post feature, especially add people or circles that you want them to see

Nute the post/person on your stream that annoyed you

Google Plus Search without logging in on Firefox

Google+ Search without logging in! Search Google Plus People, Sparkles, Circles, Posts, Music, Video etc.

If you use firefox is very easy to install plugin here: 
https://addons.mozilla.org/en-US/firefox/addon/google-plus-search/