Hi Dave and welcome to the forum. I have moved this to the intro section so we can all say welcome.
Suggested starting mods ignoring cosmetic and sound improvement ( exhausts and air intakes) would be brake pads and springs/coilovers.
The 350z ecu is said to "learn" and cancel out power increases from basic mods and as yet we have nly a few options for working on the ECU.
Forced induction is pretty expensive although a few have done it. As such, the handling is the best way to improve performance initially IMO