I'm really new to rendering in blender, so I don't really know much about texturing except for UV unwraps and things like that. I only recently decided to start rendering models since I've only used my previous models for 3d printing and such. Now, for some reason, every time I try to render some image, it's just really gray and drab and unrealistic, like this (this was made with a Glass BDSF texture just so I could see how that would actually render: 
I know this is how it's supposed to look, but what if I wanted to create a nice bright scene, like in real life?