There is no definitive answer to this question, depends on the spec of the car to start with. Some cars have a great grounding to start from, therefore where you go next dictates this.
1st modification would be the driver.............fast driving course, skid pan etc. Pointless having the power and the driving skills of Bambi
Tyres, these are as important as the driver.
Handling is next, get the chassis nice and tight, includes the steering. It doesn't mean spending silly money. Just polybush what you can then take it from there. Stiffed the springs, lowered, lower c of g.
LSD or ATB, makes as much difference as power, again have all the power and no means of putting it on the black stuff.
Then you can go on from here:
Induction kit, caf, but choose wisely, some kits will sap power.
Exhaust, sports cat, decat, manifolds.
Cams.
Remaps can be a waste of money on some cars as they are only good for OE set-ups. When going the whole hog you really need a custom ecu that can be programmed 'on the fly'.
Some ecu's are adaptable so can manage induction, exhausts and some can accept new cams, remapping will only improve the torque curve and thus open the factory default parameters for nasp engines. These tend to be some Siemens type, not all.
After that you get into turbos, superchargers etc, then you may as well have an engine transplant and go for something that has more scope for power to start with.