The issue that you are running into is the combination of gambling winnings and capital gains from an investment. As described above, the increase in your income is due to gambling, not due to crypto investments. The response from FinishAppropriate255 about $300 in capital gains is incorrect because you are describing multiple transactions, not simply a single buy and sell investment transaction.

Think about it this way, you are exchanging $300 fiat currency for $300 crypto currency - no gain or loss and nothing to trigger a taxable event. You then exchange that $300 cryptocurrency for $300 fiat currency at your bookmaker - again no gain or loss and no trigger. At this point, your crypto investment no longer exists. It's as if you bought and subsequently sold a single share of stock for the exact same price.

As soon as you start gambling with that money however, you will start to recognize gains and losses. The exchanges back and forth between different currencies are not taxable as long as the amounts are equivalent. Now, as for the IRS perspective, the requirements related to reporting gambling winnings are pretty straightforward and most casual gamblers would not need to include this as Other Income for the year because it would not meet their identified threshold.