you should save it as a .PNG and the render is a bit small. like you i jst started making my own renders so practice makes perfect mate. see you at the top some day
its ok for your first try, alot of choppyness around his leg and arm and next time make it a transparent PNG,
theres no point now... if he takes off the white background it'll leave a white outline. but when you press delete the first time keep the selection and get the magic eraser to make it transparent. then each time you press delete it will automatically go transparent.