Google+ circles are how you organize people you want to see on Google+. What circles you need depends on how much you want to be able to filter what you are reading or control who sees your posts. New Google+ users sometimes seem intimidated by having to decide what circles to make and who to put where, so I will tell you all a secret that is likely to make Google+ purists and power users freak out: You only need one Google+ cirlce. That's right. I'll say it again:
You only need one Google+ circle.
If you don't want to have to worry about managing a bunch of Google+ circles just make one. Call it "Everyone" or "All." Heck, call it "Sassafras" or "Indiscriminate Avocados." When you only have one Google+ circle descriptive labeling isn't very important.
Only creating one Google+ circle works if you don't mind reading posts from everyone you follow in a single stream. What you've basically created at that point is a version of Twitter without a character limit. To extend the Twitter analogy, to have your Google+ account behave like a public Twitter account make publish all your posts to public, which will allow anyone who follows your or who looks at your account to see the posts. To make your Google+account behave like a locked Twitter account publish all your posts to "Your Circles" (or to whatever you named your circle since you only have one). Doing that means your posts will only be visible to people who have you in a circle and who you have in your circle.
Of course, there are there are good reasons to create multiple Google+ circles. I'll be writing more about how to decide what Google+ circles to create in the next week. In the meantime though you can get started on Google+ with just one circle. Not sure who to put in your one circle or how to get others to put you in theirs? I'm writing about that next!