Depends,
How hard core do you want to go?
remove the interior, power steering, a/c, light battery, FAL windows, carbon panels, etc...

But what is your gain after all that?
A.) An uncivilized car
B.) An uncivilized car a few tenths faster - maybe.

You just have to weigh the options, and make the decision.

I would concentrate on removing unsprung weight, rotational inertia.
Light wheels, no huge heavy crap.
Maybe some pulleys, the a/c and power steering still goes

Increase power, that will accomplish the same result if you are going after a lower power to weight ratio.