In order to use Johnny Cage effectively, you have to be proficient at footsies and spacing. That is to say, you must learn how to establish a mid range game by utilizing several pokes to control space. Whiff punishing is another important aspect to implement at mid range. The key is to bait your opponent's pokes, react, and then whiff punish with a combo.
Or you can just herp derp with f+3.