Video Looks all grainy and rough.doesn't have that even clear feeling?

So i'm getting ready to start a vlog vlog but for one the picture just looks weird.i'm using my Nikon D5100 camera cause i don't want to buy one. I heard that it has pretty good reviews on its video quality and i've see some videos other people have done with the camera and they look really good. But for some reason mine just don't look right.i'm not sure what's wrong.

"Grainy" usually means not enough light. Add light. This could be as simple as using inexpensive shoplights on tripods. Read/learn about "three point lighting".