The best suspension upgrade for cornering?
axcuda already said it, bushings, bar, shocks.....
And TIRES like 68Cuda said. 17" because you can't get good 15" tires anymore. And if you ever what big brakes they will fit. And got at least 8" wide rim. Preferably 17x9 with 275/40/17
ALL the way around. Some body styles won't allow that. Head towards 17x8or9 Mustang rims/tires on Craiglist/Ebay.
If you can afford that just run some 15x7 cop rims and some 225/60/15 tires with a high speed rating. That's what I did.
You can even scratch shocks from that list that are over $40/ea from that list in terms of importance and amount of difference.
Then go out and get your feet wet.
Then add front and rear sway bar with an adjustable rear sway.
Then get some rear springs. Some stock height 340 or one size firmer (~160lbs/in) same size on both sides. If you want something better then Hotchkis rear leaf.
Then add some better shocks and expensive shocks like bilstein/koni/QA1.
Stock disk or 11.75 upgrade stock disks are fine for autocross. If you want to do much time on a road course you'll proabably want to upgrade to 13" disks with a ARengineering brembo setup or Willwood 6 piston type.
