Gaming CPU Advice

My PC bit the dust and I'm thinking about buying/building a PC that is capable of gaming.

I know graphics cards were insane for awhile but crypto prices have gone way down so I'd think graphics cards have as well

Saw some computers from iBuyPower on Best buy but never heard of them.

My main ?s are #1 is building your own still cheaper and if so how easy is it and #2 what kind of budget do I need? (probably going to hook it up to my LG OLED so I know I probably need a fair healthy budget for 4K)