I'm currently build a PC myself and have been doing some research and looking around.
(these are all usd to euro calculations so if there's any differences with the markets in Europe vs US sorry)
- Case: it seems that a large majority (or a vocal majority) of this community seems to favor the fractal meshify c and in fact that is what I've decided on. I've also looked at the Phanteks Enthoo M which has an external bay (if you need it for DVD/Blu-Ray). This is generally going to be the most flexible thing in the build if you're not super hardcore into temperatures etc. The 2 cases I suggested are about 90€
-CPU: If you're mainly aiming to game and the work station you need doesn't extend to video editing or other intensive programs I'd go with the i5 9600k at 240€, however I've heard arguments to go up to the i7 8700k for future proofing at 340€, but you should be fine with an i5 9600k
-GPU: the 20 series of graphics cards (e.g. rtx 2060, rtx 2070) are a bit over priced, but if that's all you have access to that should be fine. The GTX 1660Ti also recently released and people claim it is one of the best budget GPUs available. It hasn't been around long enough for me to make any judgements, but if you're not looking for cutting edge it's not a bad choice. gtx 1660Ti is ~260€, rtx 2060 ~320€, rtx 2070 is 440€. I wouldn't go higher than a 2070 as that would probably break your budget. If you can pick up a 1080 or 1080ti for a reasonable price on the second hand market I'd recommend going with that over the 2070.
-RAM: 8x2GB is pretty much the standard nowadays at about 90€. There's very little difference between the mHz for your purposes so go with any number as long as it's DDR4. Alternatively go here https://downloadmoreram.com/
-PSU: Don't buy it off the black market or china. Minimum I'd go with is 550 watt, but I'd recommend going 650 or 750 if you ever decide to OC. I'd also go with either full or semi modular (it's worth it for the cable management). ~50€-100€
-CPU Cooler: If you don't want anything fancy a noctua 120mm fan will work just fine. ~50€
If you go
CPU: fractal meshify c
GPU: rtx 2070
PSU: 750 Semi modular
CPU Cooler: Noctua 120mm cooler
it'll be ~980€, leaving you about 500€ for monitors.
Monitor: if you're not planning on gaming on these 1080p 60hz is fine for 3 work/browse the web monitors. I wouldn't worry about panels, TN is pretty common, but not that great and IPS is great, but fairly pricey.