You'll get plenty of advice, some of it no doubt contradictory, on the monitor decision.
What resolution and refresh rate you choose will very much dictate how powerful ( and expensive ) the graphics card will need to be. For example a GTX1060 or 570 class of card would be an excellent match for a inexpensive 60Hz 1080display. If you choose to go for a-say-144Hz 1080 monitor I'd suggest a much faster card-GTX1070/Vega56 as minimum with a GTX1070Ti/GTX1080/RX Vega 64 as upper sensible choice along with an Intel build for maximum performance ( Intel has a significant advantage with fast 1080 displays ).
Move up to any 2K ( 2560x1440 or there abouts ) and the GPU requirements shift to a minimum of a GTX1070/RX Vega 56 for 60Hz with the more expensive GTX 1070Ti and above required to give a fast display of this resolution any kind of workout. At this rez, and above the CPU choice is far less important, although Intel often has a small, advantage it is just that; Small.
And your homework for tonight is to read this:
https://www.tomshardware.co.uk/monitor-buying-guide,review-33576.html
Be sure to read it all, Daniel San, Myagi test you tomorrow.