Clical Piano Question?

I am teaching myself piano and I have just finished learning Beethoven's Fur Elise (I know everyone learns that one) I am now at the point where I can play the song all the way through and now it's just a matter of repetition until it becomes comfortable. I have a whole bunch of sheet music and I wondered about a good recomendation for the second piece I should start learning, I don't wanna try something too hard and get mad and give up. Maybe something by mozart in C or G? or is he too fast? ...I dunno, if any of you play or teach piano and wanna type down an idea or two I would appreciate it.