My thoughts on best bang for your buck would be Tune , Gears , Hooker
wait did i say hooker out loud wait did i just hit submit ...... ahhh.....DOH

I'm sure you meant Hooker headers, just hit submit too early right ?

yahhhh ....awkward silence.... yah Headers thanks Apocalypse

lol

Well were do I start? Here is some of the things I have done to my 2005 4.0L. Dual Magnaflow Exhaust, MAC Cold Air Induction Kit, Brenspeed SCT Tune, PowerSlot Rotors, Sec-D Projector Headlights, Coyote Raxiom Taillights, Ducktail Spoiler. Recently bigger tires 235R16 and am looking at new rims before the 35th International Mustang Meet in Richmond, B.C. 28 August to 01 September, 2014. I have a two page list of things I have done, these are just the major cost items.

for fairly good results at a decent price I would say gears, CAI and a tuner.

Tune, CAI and gears are best start.
the rest should be thought out, based on how far you plan on going and what direction.
you plan on, many ways to build a car. there is not limit :)

Absolutely right! Big difference in mods between N/A or Forced Induction

If you talk about Fox Bodies, the best add on would be subframe connectors. I had them added to my 92 GT and would have never believed the change in stiffness of the car, ride and handling in general. Its almost like a slot car now.

Yuup, Afgter my Doral tire went flat on the highway and i threw on the spare which was the only useful ting in the trunk, since i got the new tires (BFgoodrich Supersports run flats,) Did my own vette spare delete, world of difference without that little thing!