As a broke grad student, I did the same; except, I never really bet anything. I would put $20 in the slot machine, and promptly hit the "drink service" button. Once the drink came, I'd hit the "cash out" button, collect my $20 and move on. I know this sounds terrible, but (a) I didn't have the spare cash to throw away at the casino, and (b) I didn't have the skills to actually play any of the games where skills counted (like poker or blackjack).