how about you just worry about getting your Ls before you even think about what car you are going to get.
i think that you should wait before you get a skyline. its just too much car for a new driver. i would never get in a skyline with a new driver, i value my life too much.
my first car was an alfa 75, which i drove for about 2 years. when i first got it i thought it was the fastest thing ever and that it handled on rails. it was good experience before stepping up to a skyline.
plus if your going to have a crash, which unfortunately is very common for p plate males, i'm sure you would rather be going 40 around a corner in a datto than 180 into a pole racing someone (cause that is what your going to be tempted to do).
just remember there's plenty of time to get a fast car.