VR is NOT necessary. You can buy just the controller itself. here is a link https://smile.amazon.com/Leap-Motion-Controller-Packaging-Software/dp/B00HVYBWQO/ref=sr_1_2?ie=UTF8&qid=1505761381&sr=8-2&keywords=leap+motion
Depending on where you look you can sometimes find the controller for a cheaper price.
extra info you will need for getting started
In addition to the controller, you also need to download some free software for your leap motion.
If you are going to be mounting the controller on something and using it for VR, then you might want the free Orion download. Please note that Orion is still in its beta stage. https://developer.leapmotion.com/orion/
If you are just going to put the leap motion on the table and not use a lot of VR, then you can use the Version 2 (V2) download. These are the software programs for leap motion. https://developer.leapmotion.com/sdk/v2/
However, both downloads should work for most of the apps as they are essentially the same. The Orion is just the newest software update for leap motion designed for VR apps.
Also, please note that when you download apps from the leap motion gallery they will NOT show up in your app home as the app home is not necessary for the leap motion to be used with software from the gallery. You will treat downloads from the gallery the same way you would treat other independent programs that you normally download for your computer.