more horse power

i have a 65 lemans w/ 389 and holley 4 brl. what is the easiest and best and most inexpensive way to add some horsepower. i am yet in a situation to throw alot of money into it. what would yall recommend? thanks yall?

Get a nice camshaft, those depending on the type can raise the hp by about 25.

As previously mentioned, camshaft. Also, add 400 large valve/small chamber heads and a '68-'71 factory intake (or Edelbrock Performer) with a nice Q-Jet. HEI ignition (from any '76-'79 Pontiac V8), Hooker Comps or SuperComps (the latter being a LOT more money). Highly recommend Comp XE262H for a nice streetable power band and idle quality. The 389 is a good engine, but the later stuff breaths a whole lot better, and is still fairly reasonable in price, avoiding the "Ram Air" moniker.
Above all else, be sure you approach it with a relatively low RPM range (up to 5,500). If you build it like a Chevy, it won't live. If you build it like a Pontiac, it will smoke the Chevys and live, too!