Is the $1000 just for your sorority (because you don't have more $$$ to spend) or for every sorority?
My sorority also had a tight budget. The sorority rush budgets were capped at $2400, but we didn't have $2400 to spend (since we were a small chapter and didn't want astronomically high dues
), so we had to put together high-quality rush parties with about half the amount of money. It wasn't easy.
One relatively inexpensive thing you can do is a mocktail party. Virgin daiquiris, sparkling cider, that sort of thing. We did this one year as an informal rush event, and got a good number of people.
Good luck!