You'll want at least 16 GB of memory.
If money is tight, at least 12 GB.
Pretty much any modern processor will do for adventure games.
I'd get a Ryzen, but it's up to you.
At least a quad core for a gaming machine.
You may want both a hard drive and an SSD. If you need a lot of disk space for storage, hard drives are still less expensive per GB. SSD's are faster and some games recommend them, but some games are really large.
The most important thing is the video card, and you'll need a power supply that provides enough power to support the video card along with the hard drive, the rest of the computer, and any USB peripherals you plan to use.
As for which video card, check the "recommended" system requirements of the most demanding game you play, or want to play. Usually you can just type the name of the game and the words "system requirements" in a search engine. You may see something like these, which are two sites I often use:
So those websites recommend
VIDEO CARD: NVIDIA GeForce GTX 770 or AMD R9 280
You'd want a card at least that fast to play that particular game.
For something like Quern, https://www.systemrequirementslab.com/cyri/requirements/quern-undying-thoughts/15090
Graphics: AMD Radeon R9 270 HIS IceQ X²
or nVidia GeForce GTX 950
You probably want a video card with at least 4 GB of video memory if you're playing any demanding 3D games.
I don't know what the most demanding adventure game is these days. Most of what I play now is the Carol Reed games and pixel art games like those from Wadjet Eye, and a few casual games -- games that run fine on computers over 10 years old. Motion sickness saves me a lot of money.
So a lot depends on what you play, but you want to plan for the most demanding game you want to play, not the average.
Draclvr would probably know more since I think she still plays modern adventures and Darkside games.
New graphics cards aren't always any better than older ones. NVidia is notorious for rebranding their old cards, often with the only modifications being to save on manufacturing cost. So you may want to either check benchmarks for a particular card or ask in here if you're looking at a particular card. You can put the name of the card and the word "benchmark" into a search engine.
For an example, here are two similar cards by different manufacturershttps://www.newegg.com/Product/Product.aspx?Item=N82E16814125963https://www.newegg.com/Product/Product.aspx?Item=N82E16814125906
You can type
GTX 1060 vs Radeon RX 580
into a search engine and find benchmarks or comparisonshttp://gpuboss.com/gpus/Radeon-RX-580-vs-GeForce-GTX-1060https://gpu.userbenchmark.com/Compare/Nvidia-GTX-1060-6GB-vs-AMD-RX-580/3639vs3923
You can also check older cards versus new ones of the same manufacturer to see if the newer one is really faster. Video memory won't effect the speed of the benchmarks, though it may effect whether you have a slowdown when playing your game for hours.