What constitutes "bang for the buck" is subjective, but we'll assume you're talking about getting the most "time on game" for a given gambling stake. For that, there are three things to consider: the game's edge, the average wager size, and the speed of play. In a nutshell, the best combination of a low house advantage, a small minimum bet, and a slow rate of play will make your money last longest.
Of those three considerations, speed of play is usually most important, and it's something that you can control. There are two general rules of thumb: Tables are better than machines and full tables are better than empty tables. In other words, your money will last longer when you play table games at full tables where you're getting fewer decisions over the duration of play. By definition, this leaves out all machine games -- even video poker with good schedules -- as they simply play too fast, leaving you vulnerable to a bad run. As you'd expect, blackjack is the best table-game choice. However, you have to make sure that you're playing a game where naturals pay 3-2, as opposed to the 6-5 payoffs that are proliferating.
Blackjack is good, but it's still not the bang-for-the-buck champ. The absolute best way to get action at the lowest cost is with a sports bet. The casino has a 4.5% edge on an 11-10 sports wager, which works out to an expected loss of 50¢ on an $11 bet. Divide that by the three hours it takes for a game to be played and you wind up with a 17¢-per-hour expected loss. You'll pay 30 times that rate just to go to a movie. Want to bet $110? Mathematically, your expected loss is less than $5, and again, that's for three hours of action. The cost is $24.75 for a $550 bet and $49.50 to bet $1,100. Of course you win or lose in the full amount bet, but that's some serious bang from a mathematical standpoint.
If you're interested in reading more on this subject, check out Jean Scott's The Frugal Gambler, which includes a reprint of an article Anthony Curtis wrote several years ago titled "The Price to Play."
