agree with everyone as far as what engine is being upgraded.it also depends on what kind of HP you want to gain cause honestly...intake,header and exhaust will cost alot for a very minimal gain in HP but if your looking on more upgrades then those 3 are a good start.
i actually look at intake,headers,exhaust and chip to be a more complete level one upgrade.chips and/or handheld's will give you more HP gain when added with intake,headers and exhaust.(depending on engine)