We not only had to run recruitment on a shoestring budget, we had to compete with 4 other sororities, each of whom could spend the full $2400 or so that we were allowed. (We had less than $1000, being a much smaller group.)
We got refreshments at Costco. This included powdered drink mixes and snacks (we could serve finger food and any non-alcoholic drink at all rounds).
One year, we got our bid day t-shirts on the cheap from another AEPhi chapter. The printers had accidentally left out a color, so that chapter had them re-printed, but you couldn't really tell there was a color missing, so they let us have them at like $5 each, and they looked fine.
That does give me an idea though - could you get together with another nearby Kappa chapter and order rush and/or bid day shirts together for a volume discount?
If I think of any more ideas I'll let you know. Good luck!