For a street car I like to do the following combo:

Intake / Exhaust / Iridium Plugs / Pullies / Ported Throttle Body / Manifold Gasket.

Most of these focus on shifting the entire power band up rather than moving all of your power to the higher rpm range. By keeping all of your OEM torque and adding power everywhere in the rev range, this makes a really good combo for a street car.

Then I would bundle the following together as a combo....

Headers, Cams, High compression pistons (if your motor is low compression stock), and a tune to match

The reason I bundle these together is that usually people don't do this as a package, and end up with a car that is overcammed , or has too big a header for it's current compression or camshaft and ends up untuned (with the factory ECU unable to shift the fueling and powercurve to the right since these are RPM specific mods) and you end up with a poorly running car.

Do them together and you have a beast of a car.

I'm a boost addict myself... so before you get into the header / camshaft / compression / tune stage ... (let's call it stage 2) ... you'd want to think about boost first ... so you don't end up installing and removing parts when you go turbo or supercharged and end up wasting your money.