Quoting: Adamfx990For Linux builds, I tend to favour AMD CPUs as the multi-core performance is generally more useful and they dissipate heat a lot better than most Intel CPUs. :)

yeah, but singlecore perf still dominates when it comes to gaming, but ofc if you pair your cpu with lowend 1050Ti then it doesnt matter that much. But Ryzen for sure is more futureproof when you can get more cores with the same money.. that 10-15% weaker singlecore perf (mostly due clock speeds) is not really a issue unless you have GTX 1080Ti.

and yeah like i said before, more cores gives more breathing room for OS also if game utilizes few of them and OS can use the rest. Better for multitasking etc

Adding my own voice to the comments earlier:

If you are severely restricted on finances, then I personally would try to find something secondhand, e.g. a Core i5-2400 system that someone is letting go for $150 and then put some semi-decent graphics in that, e.g. GTX1050ti 4GB, GTX1060 6GB or AMD RX560, RX570. At least the graphics could then shift to your better machine when you can afford it.

If you really want to go latest tech which is upgradeable in the future, when you can afford it:

Recommend the MSI B350 MATE motherboard for Ryzen CPUs (about $100). Get whichever Ryzen you can afford, with prospect to upgrade it in the future. I personally really like the Ryzen 5 1600 which comes with the Wraith cpu fan, and is good to overclock (and lots of cores, about $250). Recommend get a single stick of 8GB DDR4 RAM, and potential to upgrade with 1-3 additional DIMM modules in the future. Noting that this motherboard also has a NVMe slot for really fast solid state drive in the future too.

Then once you have the machine based on Ryzen, as per above, get what graphics you can afford (even, say a secondhand GTX960 or GTX750ti or whatever) and use that until you can afford better.

g000h's above suggestion is really great if you're on a budget. I have an i5-2400 system with 8GB ram / GTX 760 which still packs a punch in today's games. I checked a few benchmarks and it seems to be on par or slightly slower than the Ryzen 1200, not bad for a 7 year old CPU.

Considering how you seem to be aiming for an i3-8100 in the first place, it would be a good idea to look for a used i5 system, that way it might leave you with some options such as better GPU or a cheap SSD.

I have seconds thoughts about the nvidia and thinking I would like to have amd with mesa instead. the RX 560 (4GB) has about the same price as gtx 1050ti. How much worse would you think I will be with it? (currently I am planing to buy in three weeks, hope the prices fall a bit more)

RX 560 is decent, but actual result depends on your native resolution.

Quoting: ShmerlRX 560 is decent, but actual result depends on your native resolution.

If you ask about the monitor, as I said I am only interested in 1920*1080

Quoting: lucinosIf you ask about the monitor, as I said I am only interested in 1920*1080

That would be fine IMHO.

Excuse me for asking again, the question is how would you compare a RX 560 and a GTX 1050 (Ti) for gaming on linux. (How much more or less problematic is any choice and how much worse or better is the performance.)

if you are going to be using KDE, go with AMD, it has issues with nvidia drivers. As for Gaming i think you will have slightly better experience in terms of support and performance with nvidia.
So basically its all up to you which you want. Both should be fine enough with both their own small issues

Some advice from me, and I build lots of PCs.

My preferred price/performance is the Ryzen 5 1600 which comes with the Wraith cpu fan.
My preferred motherboard is the MSI B350 MATE which works very nicely with the Ryzen above.
(You can overclock the 3.2GHz R5 1600 to 3.6GHz on the Wraith, no problem, on this board.)

This motherboard supports 4x 16GB DDR4 RAM (I tend to go for 2400MHz speed, for value for money.)
This motherboard has a NVMe PCIE SSD slot, for getting 5x speed of SATA SSD drives with the right SSD.

I am using the above components with an Nvidia GTX1080TI on Debian Linux 9.x - no problem.

Recommend Nvidia GPU with as much speed and RAM as you can afford, e.g. GTX1060 6GB (not 3GB).