Your Light Source is off...in the render the light is hitting the guy from the right..while you put it in the left...try dodging/burning...etc...to make it work properly.

Your guy(render) has stroke on...either badly cut...or you put it on there to hide the edges...which looks bad, get rid of it.

And right now it seems like, background, add render, add 2 different c4ds on top if it...and a little light source...you gotta put more time into making your tags, and thinking how things work out mate.

Keep it up though, don't quit.

Oh and keep on reading tutorials...to get the basics.