If you’re required to pay tax, then your next step would be to keep accurate records. It’s important to understand the tax rules of the country you’re gambling in. Most gambling rules levy taxes not on winnings, but on profits. In Germany, which instituted a gambling tax in 2012, you're taxed 5% on any profit. If you live in Australia or New Zealand and win money when gaming, you pay no tax. If you live in Canada and win money when gaming, you pay no tax providing you are not a professional gambler. If you are in the UK and win money when gaming, you pay no tax. If you live in the US and profit from gambling, there’s usually a 24% tax.
Tax rules concerning gambling vary a lot from nation to nation.