Ideas that quickly came to my mind:
-Hire a homeless person(s) to do something, even if only to set another process in motion.
-Commission a small work of art in my name or for a theme/cause of my choosing. (Find a starving art student)
-Advertise something online that will surely draw people: i.e. FREE BEER to move the maximum amount of people to a desired location in as little time as possible. Twenty dollars ought to be able to buy about 50 cheap beers.
Access to a crowd can be converted into further power.
What if you had an advertiser pay you to promote their product at your giveaway? Big corporations aren't likely to negotiate with small timers. Perhaps a small to middle size business would be more amenable?
Advertise for a sponsor before the giveaway. See who's out there.
-Exerting the maximum amount of leverage and influence/unit of force
-Exerts the given force in a way that achieves the net gain of force.
-Ripple effect: exert force in a manner that causes a chain of desired consequences. Do as much as possible with one exertion.