$400? What is that money for?
If its for EVERYTHING...I would just say get a bunch of cases of cheap beer and some bottles of cheap shit and open the house up.
Or have a pig roast/BBQ at the house. Have the brothers pitch in $5 or $10 each if you need it. They should be willing to.
I would focus on just getting a lot of flyers and info out there. Get large color signs that give good information on when where and how to rush and explaining the advantages of greek life in a way that a freshman would understand. Leave it up to the fraternities themselves to give out free stuff. Maybe have keychains or something to give out during the day during rush and encourage freshman-looking guys to go out and rush and give them a flyer as well.