For an RPG fan like me The Witcher franchise is an absolute godsend as its one of the rare few modern RPG series that manages to have its story perfectly thread the "gray area". The characters are nuanced, the plot is intriguing, and the choices you have to make are never as simple as "save everyone because you're a true hero" or "kill everyone because you're a completely demented psychopath".
If you're interested in this sort of an RPG but have never actually played The Witcher series, I'm glad to tell you that the franchise is currently 50-85% off on Steam. Naturally, the biggest discounts are reserved for the older games, but they are all well worth playing regardless of their age.
As for my recommendation, I would probably start with The Witcher 3 or 2, depending on your budget. And don't worry, you don't have to play any of the games in the series in order to understand what's going on, they all tend to have fairly well-contained stories. That disclaimer aside, the reason I would recommend these two over The Witcher 1 is because they feature your standard action-RPG mechanics and combat, things you've probably seen in numerous other games, so they should be easy to adapt to and enjoy.
However, if you don't mind button-mashy combat and an utterly terrible introductory section then I would also recommend you play The Witcher 1. In my humble opinion it contains the best overarching story in the entirety of the series, with the end "twist" being so mind-blowing you're going to want to replay half of the game in order to see if all of the pieces fit together... and before you ask, they really do!
This promotion will last until August 26th, so if you feel like playing some amazing RPG games on the cheap, give The Witcher series a try. Its one of my favorites, so hopefully you'll be able to enjoy it as well. Have fun!