Exchange-traded funds offer a convenient way to invest in sectors or niches that interest you. If you expect the gambling industry (or "gaming industry," as it likes to call itself) to thrive as more casinos are built around the world and people continue to take risky chances with their money, the Market Vectors Gaming ETF (NYSE: BJK) could save you a lot of trouble. Instead of trying to figure out which companies will perform best, you can use this ETF to invest in lots of them simultaneously.

The basics
ETFs often sport lower expense ratios than their mutual fund cousins. The gaming ETF's expense ratio -- its annual fee -- is 0.65%. The fund is fairly small, too, so if you're thinking of buying, beware of occasionally large spreads between its bid and ask prices. Consider using a limit order if you want to buy in.

This ETF has performed reasonably, but it's also very young, with just a few years on the books. It outperformed the S&P 500, on average, over the past three years. But as with most investments, of course, we can't expect outstanding performances in every quarter or year. Investors with conviction need to wait for their holdings to deliver.

With a low turnover rate of 19%, this fund isn't frantically and frequently rejiggering its holdings, as many funds do.

What's in it?
Various gaming companies had strong performances over the past year. Melco Crown (Nasdaq: MPEL) gained 76%, benefiting from the fact that it concentrates on Macau, where casino companies have been thriving. Other casino operators, such as Las Vegas Sands (NYSE: LVS), up 26%, operate both there and in Las Vegas, where business has not been booming in quite a while. Both companies offer investors reasons to be optimistic, but Melco Crown sports a more compelling valuation.

Other companies didn't do as well last year, but they could see their fortunes change in the coming years. Wynn Resorts (Nasdaq: WYNN) shed 5%, and has some doubtful of its expansion plans in the U.S. Its overseas plans seem more promising, but there are signs of possible slowing growth in Macau that can spell some trouble for Wynn and others. MGM Resorts (NYSE: MGM), meanwhile, lost 2%, burdened with a lot of debt that it took on as it expanded in Las Vegas, where its City Center isn't yet delivering big bucks. One potential catalyst that could help MGM and others is the legalization of online poker -- but that hasn't happened yet.

The big picture
Demand for gambling opportunities and venues isn't going away anytime soon. A well-chosen ETF can grant you instant diversification across any industry or group of companies -- and make investing in and profiting from it that much easier.

Learn about the 5 ETFs That Could Soar in 2012. And if you're looking for some great investments beyond ETFs, consider these 12 Dividend Stocks for 2012.