IRS Publication 54
http://www.irs.gov/publications/p54/ch04.html#d0e2133
"your tax home is in a foreign country and you meet the bona fide residence test or the physical presence test, you can choose to exclude from your income a limited amount of your foreign earned income. Foreign earned income was defined earlier in this chapter.
Yyou cannot exclude more than the smaller of:
1.$80,000, or
2. Your foreign earned income (discussed earlier) for the tax year minus your foreign housing exclusion (discussed later)."
Gambling however, appears to be considered unearned income, as shown on the chart in pub 54