1) Lightroom likes fast processors. Period. i7 at 4ghz is good or anything in that ball park. This is the most important component, little else makes a significant difference unless you really cheap out on components.
2) SSD for operating system, programs and Lightroom catalog. Regular 7200rpm hard drive for image storage
3) 16gb memory minimum, 32gb if you also have other stuff like photoshop open
4) Graphic card is not currently used much by Lightroom but that is changing. Get a decent one but don't waste money on anything high end
These guys actually do benchmarks on Lightroom and build PC's based on that:
Recommended Hardware for Adobe Lightroom Classic CC - Puget Systems
Brand makes little difference these days, just make sure you know what is under the hood.