Um, set a goal, then make your plan.
Things to ignore on a pushrod V6 motor:
Cold air intakes
Anything higher than 87 octane unless you are using a power adder (supercharger/turbo/nitrous)
Throttle body upgrades (unless using a power adder)
Throttle body spacers
X vs H pipe doesn't matter b/c of the firing order
Skip anything that applies to a 4.0L SOHC motor - as they are completely different than your single port 3.8L OHV.
Want big power, skip the bolt ons and just put a supercharger on it. You will nickel and dime yourself to get minimum power gains if you screw around with bolt ons.
I build cars from the suspension/brakes up.
1998 Roush: M112'd Aluminum block 4.6L 2V 6 speed track car
1999 SVT: Mostly stockish
1970 Mach 1: Resto-modded monster
2000 Roush #5004 - World's FIRST M112'd V6 Mustang. Sold, but not forgotten.