You will get many recommendations for the new ryzen 3000 series processor.
Many many threads for not much.
But, from the reviews I see, Intel is still up front for gaming.
That is because most games can not take good advantage of more than 4 threads.
I think that is particularly true for sims, mmo and strategy games which tend to be cpu intensive and depend on good single thread performance.
Depending on your budget, I think perhaps a 6 thread i5-9600K or 8 thread i7-9700K will be the best along with a Z390 based motherboard.
Budget about 2x the cost of your processor for the graphics card.
If in doubt about the graphics card, buy a EVGA card .
They have a 90 day free upgrade option if you should decide you need something stronger.
Consider the case carefully. Looks count. Buy a case you love, it will be with you for a very long time.
Past looks, my criteria would be good front intake capability.
That would be at least two 120/140mm front intakes. If they are filtered, your parts will stay cleaner.
I like 160mm available for an air cooler.
An example might be the Coolermaster H500
https://www.newegg.com/gunmetal-cooler-master-mastercase-h500-atx-mid-tower/p/N82E16811119350
Avoid liquid cooling.
In a good case, a tower type air cooler will perform just as well, be less expensive, quieter, require no maintenance, be easier to install, and... will never leak.
Buy a SSD for windows. 500 or even 1tb. Samsung evo would be my choice for performance and reliability.
One can always add a HDD for bulk storage later.
On a budget, bypass the pcie versions which are more expensive.
The monitor is another long term purchase.
For your type of games, pick a larger IPS panel.
You get better image quality and sufficient performance.
tn panels are best for fast action shooters.
650w psu will run any modern graphics card. The evga g3 is a good unit.
An alternative might be Seasonic focus.