If you are just getting into trackdays. Aero is one of the last things you do. Take that money and get some face time behind the windshield.
If you are getting the splitter for looks. Knock your socks off. There are others things that you could do to improve the Z for the track. Once you start down the rabbit hole of trackdays. It gets deep really quick. So plan your mods to your skill level. It will save your wallet and your sanity.