Casino Royale on the strip has some of the cheapest gambling. They also have $1 Michelob beer and $1 Margaritas! Another decent place to get drunk and gamble cheaply is O'Sheas beside the Flamingo. They also have beer pong!
The hooters casino just off strip beside the tropicana also has pretty cheap gambling...and hooters girls as cocktail waitresses!
There are those 'Fat Tuesday' stands at a bunch of the casinos, that sell the huge 3 foot margaritas...now they're pretty pricey, but delicious. However, a little trick: What they typically offer you is $1 for an extra shot. You can get up to 5 extra shots @ $1 each. One of those Monster Yards with 5 extra shots and you'll be blotto by the end of it.
Downtown check out the golden gate for 99 cent shrimp cocktails (if you have one of their players club cards).
Most downtown casinos have really cheap drink specials and food specials as well!