First take time to plan for the food. Write down what you would like, and also in that write down what you are willing to make yourself. Remember the more you are willing to do, the more money you will have in the end.
Making a list, you can break into two parts. One is for decorations and items you may want to have in the way as favors. On this list you can add your paper plates and your napkins and utensils. All these you can get at a party store. Most times the party stores are cheaper for these products.
The other list is for you to purchase food. Simple items you may want to have at a graduation party are finger sandwiches. By taking a large loaf of bread and cut off all the crust. Make the sandwiches on whole large pieces of bread. Then you can cut them in four and get four out of each large sandwich. On this list don't forget to purchase your ice and soft drinks. Chips are also great fillers and pretzels.
By taking time to plan you will have money left over. Well not really am sure you may have to foot some to the new college student.