Hello Nathan and welcome to the forum.
We all started somewhere and it was not always the best..........so don't sweat it! As Argos poiinted out, the lighting was the first thing I noticed when I saw the composite. If you look at the trees in the background image (album) you will see that the light source is originating from our right hand side and the shadows are on the left. The lighting on the guy (J. Cole) is just the opposite and missing his own shadows.
Like Argos I feel that the selection of the guy is too soft. The edges need to be a little more crisp.
I also feel like the guy is a bit too small and therefore not quite in proportion...............but it's hard to tell with the poor quality of the distorted car in the BG image.
The overall lighting is too dark. A common manifestation for newbies is creating dark images. Dark has a tendency to cover and hide mistakes, unfortunately it obliterates detail.
Original lighting.
Keep up the good work.......you're off to a great start!