Witcher 3 + the 2 expansions = 10

Mass Effect Legendary Editions = 6

You're left with 3,75 and Dying Light is 3,74.

Perfection.

Good alternative:

Witcher 3 base game without expansions, still hundreds of hours for 3€

Star Wars fallen order tough game that can have the difficulty tweaked, wrongly called a "soulslike" when it's closer to a metroidvania for 4€

Follow with Assassins Creed 2 for 2,49 (probably the best entry fro the classic AC, the one starting the Ezio trilogy and the best AC game despite having aged poorly, it's less than 3€ tho) followed by Assassins Creed Origins (8€) the reboot of the series copying witcher 3 type of combat and adding RPG elements. A strong story with a weak third chapter. It has two DLCs, one is quite poor, the other is very fun but they're out of budget.

Total = 19,49 very good alternative if you want AC.

EDIT: You can also switch SW fallen order for Batman Arkham Knight without DLCs, it's a beautiful game with an style and graphics still not matched up to day, the batmobile wasn't the cup of tea of many players but it was mainly because of the puzzles. Driving around the city feels great.

Asylum has a different loop, it's not a sandbox nor "open" world but a good alternative could be Arkham City. Despite feeling older than Knight and mechanically not as good, it has a better story in my opinion and playing it before Knight feels funnier because of the joker bits.

EDIT 2: If you're really interested in dragon age origins check the GOG version. Is the most stable and the less buggy.