If I were you, start learning what Jepp charts are about. Invaluable info and you can save a lot of time. Revise your radio calls, eg the Mayday one, know the order/sequence of prioties. If you are still feeling keen, start learning and understanding piston engines and turbines. It would be well worth the effort to get yourself to a maintenance hangar and actually look at the guts of an engine. It makes the theory a lot easier when you know how it fits together. Since piston and turbines are examined, it doesn't really matter. Both is perfect. That should keep you busy. If you can, pop over to an aviation museum where they have cut aways of engines and wings etc. Being able to visual what an axial engine looks like v's a centrifugal turbine is useful.
None of this is really hard work. In fact it should be enjoyable, you have enough hard work coming up.
Trust me on that one.