Effects --> Stylize --> Roughen Edges. Tweak the contrast, animate the Turbulence and you can get some pretty fiery stuff. You might also consider applying Colorama after that. Additional refinements can be done using CC Vector Blur for instance. For a trailing effect, you could use anything from Timewarp, to Echo to a simple directional blur...
For your next fireball project, use a fire preset with Particle World, precompose that and apply CC Sphere. Precompose that and place it into your video. Use Motion Tracking to attach it to the hand. Split the layer where it leaves the hand. Use Shatter when it hits the wall on the other side of the room.
After you've mastered those effects and procedures, You can precompose the Shatter layer into a 3D comp so the wall has perspective and you can add a light to the scene that might travel with the ball.