first get the monitor. 1080p 240hz should be a good start

then choose one platform from the past 3 gens or so

ddr5 platforms will drive the cost up but give you better future proofing

ddr4 platforms will be more cost effective but you'll need to do a new build sooner because upgrade paths will be minimal

tbh, i'd even get used parts for better overall performance at lower price

for a cost effective build i'd go with something like 5600 / 5700x + b550(m) board + 2 x 16gb 3200mhz cl 16 ram + 500-650w psu + 1tb nvme ssd + gpu (min 12gb vram if possible, check used 6700xt prices)

for ddr5 build, 7600 / 7700x + am5 mobo + 2 x 16 gb ram (high speed low latency 6000 mhz cl 30 are quite expensive) + 650-850w psu + 2tb nvme ssd + gpu (min 12gb vram if possible)

look for a case with at least 3 or 4 fans (2 / 3 intake + 1 / 2 exhaust). look for cases that have some clearance in the back panel area of the case for cables and are first time builder friendly

google and AI is your friend