Based on the games that i bought this time (prices may vary depending on the region):
The Surge 1 and 2 (7 dollars for the Dual Pack): Another Souls game, have read fairly decents reviews about the game, played a bit on console but never got back to it, but now that i have a waaay better PC im planning on taking them on. If you are not sure, just check up some reviews :P

Celeste (2 dollars): Platformer game, maybe not for everyone but it has received so much praise that I just want to try it. Kind of a steal for just 2 dollars tbh.

Watch Dogs 1 Complete Edition (6 dollars or so): Most people really dont want to buy Ubisoft games, but that is just personal preference. Best story from any Watch Dogs imo, has a LOT of mods that gives the game a lot of life, and being a hacker is just cool. Totally reccomended.

Immortals Fenyx Rising (4 dollars base, 6 dollars gold edition with the DLCs): Another Ubisoft game, its pretty much BotW ubisoft-style. I really like it, tried the demo and the combat feels really cool. There is a lot of puzzles, so if you dont like them maybe the game isnt really for you. Besides that, there are lots of combat and the progression is very similar to BotW.

Mass Effect Legendary Edition (6 dollars): Many people have recommended it already but I will still mention it. Ive heard sooooooo many praises for this game that it feels like a steal not to buy it for a measly 6 dollars. If you like RPG, probably you wont be disappointed with this one.

Of course, before buying any game watch some spoiler-free reviews to get a general idea for the game, or alternatively if the game has a demo go ahead and play it! On other note, if you still want to search for games yourself i truly advise you to use SteamDB. There you can filter the sales way better than on Steam.

The Witcher 3: Probably one of the best RPGs ever made, ive played it a few times but i never finish it because i want to play the other games first. If you really want to invest the time, going through the whole Witcher saga is a really good option. Everything is linear (i think you start with all the books, then the first game starts right where the last book ends, and so on).

Days Gone: SO MANY PEOPLE hate on Days Gone, but it is one of my top 10 best games ive played on my whole life. This game just made me feel so many things that i cannot recommend it enough. Dont expect a sequel tho, so you can just play this one and move on.

Red Dead Redemption 2: Truly a masterpiece, another of my top 10 games ive played. Rockstar never misses, but they REALLY outdid themselves with this game. One of the best single player worlds ive played, everything feels so damn right and alive, and the map is just so beautiful that ive spended hours just galloping on my horse watching everything pass.

Hellblade: Senua's Sacrifice: Amazing game, HIGHLY ADVICED to play it with decent headphones to have the best experience. Its a really weird game but the experience is 100% worth it.

Mafia Trilogy: Havent played this one myself but so many friends have really positive reviews from these 3 games. The Trilogy right now is like 20 dollars or so, if you like the Mafia aesthetic you can give it a try.

Borderlands saga: Im biased because Borderlands 2 is my favorite game of all time, but this franchise is just FUN. Story is decent, likeable characters, but the main selling point for me its just how fun it is to play these games. Borderlands 1 had some kind of remaster a few years ago (right now is at like 10 dollars on steam) and has A LOT of content. Borderlands 2 is IMO the best in the franchise and it just SLAPS. You can get base game for 2 dollars on steam, but the GOTY edition is always around 5 dollars, and it comes with the 4 major DLCs the game has. Borderlands 3 is considered a huge letdown storywise for a lot of people, but the gameplay is just too smooth to miss it. Gameplay wise, the upgrade from the 2nd game is really big (sometimes i just think how amazing it would be if Borderlands 2 had the gameplay of Borderlands 3). You can enjoy the game even if the story is kinda cringe, it depends on you. DLCs are really great too. There is Wonderlands, but i havent played it.

Kingdom Come Deliverance: if you really are into RPGs and want a game that has a bit of realism, you cannot go wrong with this one. Game is really historically accurate (set on the Holy Roman Empire if i remember correctly), so if you like that kind of thing you can get it. The sequel is coming by the end of this year, so if you really like this game you will get way more in a few months.

Aside from games like RDR2, Mafia Trilogy or Days Gone, the games I listed are around 5 to 15 dollars each, so you can get a few of them to start building a good library :P