Professional gamblers have different rules than recreational gamblers.
Some gamblers can file Schedule C if their gambling activity is extensive enough to rise to the level of a trade or business.
This is a difficult hill to climb, as shown in a recent case (Mercier, TC Bench Opinion).
But if scaled, pro gamblers can deduct wagering losses to the extent of their winnings on Schedule C. The cost of their meals, lodging and transportation are included in gambling losses and can’t be reported as separately deductible expenses.