Polish 11 Bit Studio's popular This War of Mine is on sale on Steam. You get the full game, season pass and DLC's for 18,57€, roughly $20. Not only that, the developers will use 100% of the income for the next 7 days to help victims in Ukraine. 

There's really no questions to be asked here. Buy the game and show your support, not only to the Ukraine people but also to a developer and their game which is very much about what is going on in the world right now.

https://store.steampowered.com/app/282070/This_War_of_Mine/

"For the next seven days, all profits from This War of Mine, all its DLSs, on all stores and all platforms will go to a special fund. A week from now, this money will be donated to the Ukrainian Red Cross to directly support victims of war in Ukraine."