It is not important to buy a lens for your vlog camera. If you are just starting or you make casual vlogs, you will not need a lens as the camera itself will do the job well. However, if you make travel vlogs, you might need to buy a lens for your vlog camera. The kind of lens you use will determine the field of view of the camera and its optical zoom. Keep in mind that not all cameras support third-party lenses.  If you intend to use a lens with your camera, make sure that you read the lens compatibility of the camera before buying it.