St1 . A higher flowing air filter and free flowing exhaust.
St2. Add a bolt in cam.
St3. Up the compression or a big bore kit ( which means another higher cam grind ).
St4. Port and flow the heads. Maybe a bigger throttle body but not really nessessary.

Something like that order.

Seriously, you either stop at St2 or go direct to St3.
Cams and compression are a decision that go together, so do it once and do it right.

Have fun and deep pockets are required.

St all. Decent tune/tuner.

That was well explained by Quack. When you add performance you need to set up your suspension and brakes more. So you should allow these cost as well. You don't really get your money back on those upgrades when you go to sell either.

Is it mandatory that improvements be done in the precise order, as outlined by Quack ?

ie: If I have ONLY done stage 1 and come across a cheap as shit, bigger throttle body ....

OR, perhaps ...

I like the idea of 'free flowing heads' and have yet to involve myself in a cam ...