If you've never heard of Lensball before, don't sweat it. I had not heard that particular term used until now, either. I'd be willing to bet, however, that you've seen some of the cool shots people are taking with these accessories though.
Ilia Alexanderson's YouTube video has some straight-to-the-point tips on ways you can get started with your new toy. He makes a great point about composition and reflections (the main thing that a Lensball does). A Lensball allows you to play around with what is essentially two frames in one image, and this deliberate two-frame composition is what's going to help create an eye-catching image. You have your background, whatever that may be, and then you have your flipped scene being shown inside the sphere. Choosing an appropriate location or subject that allows the background and the reverse image to compliment each other (with lines, colors, or lighting) leaves you with a pretty sweet shot.
Something that is quite a popular image style on Instagram is a really simple concept that anyone can experiment with. If you're a fan of eye-catching images or shooting with a very shallow depth of field, this might be for you. A cell phone can do well if you're looking for a cool shot and you're in a pinch, too, so get creative.
Is this something that you've tried before? Surely you've seen these kinds of images circulating Instagram, usually rocking a sunset or ocean reflection of some kind? Personally, I think they are pretty sweet. Anything that takes something incredibly simple (a sphere of glass) and allows people to put it to work and create something that people want to see is always awesome in my book.