Not so Big Brake Upgrade

2011 Nismo#91

You just need fluid and pads and you'll be fine and well within budget.
2 Bottles brake fluid (any will do) ~25
Carbotec 1521 or similar ~300

It's completely up to you if you want to do brake lines but since your changing out your fluid it's not too much effort to replace them or you can spend ~100 somewhere else where you'd actually get an improvement.

Slotted and/or drilled rotors will give you more problems, will put a hole in your wallet, and give you no improvement.