If you're new to tracking, I'd just keep it stock.
The car is WAY more capable than most people who do track, including me. A lot ofids are just to compensate for poor driving, IMO.
Eventually, the brake pads/fluid will need upgrading, but I've been in M3's where the instructor is flying around the track in a stock car, including the brakes.
Let me get this straight... You are swapping out parts designed by some of the top engineers in the world because some guys sponsored by a company told you it's "better??" But when you ask the same guy about tracking, "oh no, I have a kid now" or "I just detailed my car." or "i just got new tires."