Whatever you do, don’t use G2A and other similar CD key reseller websites. Developers would rather you just pirate the game because a lot of those keys are stolen, which cause a charge back that ends up costing the developers tens of thousands of dollars in fees. In rare cases it has even bankrupt them.

https://www.digitaltrends.com/gaming/g2a-controversy-indie-game-developers-calling-out-illegal-key-resellers/