Hmmmm...nitrous or supercharging???
Seriously, the way I would start would be with a moderately priced intake, cam and carb kit. That way you'd have a matched set of components created by a tuner much more intelligent than you or I. I'd also add a free flowing exhaust system as well. You can also add a better ignition to give you a hotter spark (MSD comes to mind).
However, all of that won't make you happy if you have a ring and pinion gear in the rear end that is in the lower range. My 400+ HP 390 big block seems really slow because of the 2.75:1 gearing.
Above all remember, the more $$$ you spend the faster you'll go... and the faster you'll be broke!!!
Ken