how the heck am I gonna pay it forward?

the person behind me paid for my meal. I was so happy and the woman I was with was so touched that she cried. I have $32 and that is all I have for the next two weeks. i wanna pay it forward, but I am a poor starving student. how can I do it without starving? if I can do it without starving, how the heck can I pay it forward?