Quick question Racebreed, and im not trying to make fun of you. Have you ever been in a skyline with 300rwkw? If not why did you choose this number?
300rwkw in a skyline is a lot of power, and for you to jump from your previous cars to the skyline is going to be a big enough power upgrade. Once you get used to this, add some more power, maybe 200rwkw, once you get used to this and want more, maybe aim for 250rwkw and see how you like it. Don't just randomly pick 300rwkw when you have no idea what it feals like. A sudden mistake in a car with that much power will see you kick out and spin the car, trust me, i've been in plenty of cars with that much power or even more (dads monaro has 370rwkw) and when pushing them to the limit it takes a lot of concentration and skill to not get urself killed.
Your budget is not going to allow you to get all the mods you have listed like many people have said. When you consider everything you will need to make the car with that much power not be a ticking time bomb or the rest of the car not being able to keep up (ie suspension, brakes, diff, clutch).
Just don't rush into anything and get used to your own car before you set out to get a number on a dyno sheet for bragging rights but not being able to actually control the car when your in it.
Just my 2cents worth.