It's choppy because you used the eraser. When I first came here and made my first renders, I also used the eraser and they looked like yours. So what you should do is use the Polygonal Lasso Tool, zoom into the picture, and start making lines around the whole picture. That way your render will come out better.
i usually use that.......i didnt use the eraser though..i tried something new. i tried the quick mask way.....
not bad for a first... but you know... you can use a combo of a quick mask and polygonal lasso ^_^ ~ Crimsons