Take your time and plan the best route before you blow your money. Like ChevyGuy says, start with experimenting with the plugs and fuel grades first. I would then consider the tune options. Either BNR or WOT-Tuning can help you out.
[h=1]The BNR/EFI Live tune review you've been waiting for.
[h=1]TRIFECTA: +44 WHP and +51 ft-lbs on Chevrolet Cruze 1.4T MY2011-2015 (Jan2015 Update)
I would then consider handling upgrades including tires, rear sway bar and struts/shocks. With those items alone you will "feel" much more in the seat of your pants. Then maybe look into larger injectors to help increase you fuel flow. At this point your about $2200 into it.
If you are going to be on a track, then I would look into the cat-less down and mid-pipes by ZZP. You might want to add a few gauges to help you track engine performance now. A number of folks think a CAI adds a few HP, but I have personally not seen any numbers to back it up yet. A cat back (or cat-less) exhaust with the diameter the same as the turbo outlet may help, not sure as again nothing to back up claims so far.
From this point on costs increase dramatically for the most part. Better turbo, better pistons etc.
But, if you think that anything of this will turn this little 1.4 into a race engine, you should look at a different vehicle (although I did see an Aussie version that might blow your doors off.)