It's an extremely addictive and replayable deck building roguelike with poker theme. Although you don't need any previous knowledge about poker - all information you need is in the game. It's very easy to pick up but gets tough at higher difficulties, and it hits that "one more round" urge just right. Oh and it's also dirt cheap even among other roguelikes.
There's also a mobile version if you have a lot of extra time but not a lot of access to a PC.
Darkest Dungeon, Jedi Fallen Order, and Titanfall 2 are all super cheap. Darkest Dungeon pissed me off 15 hours in or so, enough to ragequit the game, and I'd still consider it well worth the current price.
Disco Elysium and the original Hades are also great buys at 10€.
If you're into older rpgs, i would wholeheartedly recommend the Gothic trilogy. Will fit just under 5$, but they're absolutely insane value for the money. With that you'll also get Archolos for free, which has blown all expectations away entirely. This mod ended up being better than a lot of big-budget titles I've played, and they've done it all out of pocket
Both Enter the Gungeon and Crosscode are 70% off right now, and some of the best games I've ever played. If you can still afford it I would throw Hollow Knight or Crystal Project in there as well.