MacBook Air RAM Issues

What's up guys, so I rather recently purchased a Haswell MacBook Air 13 inch, with 4gb of RAM and i5 processor. The first couple of weeks have been great, and with me being somewhat of a perfectionist when it comes to electronics I have spent a good deal of money on, I have been regularly checking Activity Monitor to keep an eye on things. For the first week or so of owning the machine, checking AM when the MacBook was idle gave me a readout of only about 1gb of RAM in use, this being with no apps being open or running in the background. However, recently, this number when idle has climbed to roughly 2.7 gbs, and sometimes pushing three. And when I open a very simple app, such as Spotify, that number jumps to around 3.5 gbs. I know this is not good, and was wondering if you guys have any suggestions on what may be causing this, and what can be done to stop it. Thanks!