Gambling losses are indeed tax deductible, but only to the extent of your winnings. This requires you to report all the money you win as taxable income on your return. However, the deduction for your losses is only available if you are eligible to itemize your deductions with Schedule A. If you claim the standard deduction, then you can't reduce your tax by your gambling losses. You can manually select the Itemized or Standard Deduction in TurboTax by following the Instructions in the FAQ below:
https://ttlc.intuit.com/replies/3300919
If the sum of your Itemized Deductions does not exceed the amount of your Standard Deduction, Schedule A will not be beneficial to your Tax Return.
Below is are the Standard Deduction Amounts for Tax Year 2016. Additionally I have attached a list of common Itemized Deductions so that you can make a more informed decision on you Deduction Method.