I've been reporting pool income for decades as a sole proprietor (Schedule C). The problem is that you have to show a profit in three of five years (or something like that) or they'll say it's just a hobby. Car mileage is one of the included costs. I got the advice of a tax accountant the first year I did the Schedule C.The other option, and I am not a tax guy by occupation, but I do know a fair amount about the tax laws, is that if you play in enough tournaments to generate a positive income, I believe that you could set yourself up as a business, deduct all travel, equipment ( cues, cases, etc), entry fees, lodging, etc. to help offset much of your total tournament winnings.
I've heard that some business keep three sets of books. The IRS books, the books for potential buyers, and the real books.... The IRS also likes to pose as buyers of "cash" businesses, getting a peek at the "real" books and then dropping the tax hammer on the perspective seller. ...

I don't think winnings in tournaments are considered gambling and I think the related 1099 is going to be a 1099-MISC, but I'm neither a tax account nor a tax lawyer. If a tournament promoter fails to file 1099s, he is liable for the tax on the money paid. Foreign residents get a different form and usually the tournament must withhold tax for them.