First Prime - advice needed

The pancake is only amazing because it is physically small, and good at what it is spec'd for.

If you don't mind getting something slightly physically larger than the pancake, I would highly suggest getting something with a larger aperture. Getting something at f/1.2, f/1.4 or f/1.8 (depending on your budget) will open a world of possibilities for fantastic low-light performance, DOF effects and other things that you won't get much of with the f/2.8 pancake.

In short the pancake isn't going to get you much different over your kit lens except better image quality. But a fast f/1.x lens will get you something novel, something different, a completely new animal to study. Which sounds more like what you're looking for.