You can try to do something like this
if you want it to be more solid than jello, and you could add some cool stuff like some "slime" sticking to the floor when its lifting up or something.
Also, your gif had frame overlap so i fixed that:
You could possibly up the contrast on the slime a little more, the back end seems kind of weird during the animation, and if you exaggerate the extremes of the movement a bit more I feel like it would look more impressive. Right now it seems like its moving reaaaally slow.