If you want help:
>Assemble your parts list
pcpartpicker.com
>State the budget for your build (and country if not the USA)
>List games/software you use often, as well as your monitor resolution + refresh rate
>Clarify your goal for build improvements: lower price or improved specs?
How to assemble a PC, select components & more (kind of outdated)
wiki.installgentoo.com
CPUs:
No i5 unless discounted
>G4560/G4600 - Budget builds (R5 1400 - Cheapest quad core you can get (Ryzen 3 soon)
>R5 1500x - Good but up to 1600 if you can
>R5 1600 - Best value for higher fps gaming / mixed usage; 1600x if you want higher stock clocks
>i7 7700k - 144hz only
>R7/Used Xeon/Threadripper - Compute/Multitask/VM/mixed use; Not for just gaming
GPUs:
Coin miners have driven price up and stock down, waiting to buy a GPU might be wiser
>Integrated CPU Graphics - Desktop stuff and very light games
>GTX 1050(Ti) - Lower end budget cards, drop settings on newer games, RX560 beaten by both
>RX570 - 1080p@60~hz maxed, running most maxed older games at 100~Hz
>RX580 and GTX1060 6GB - 1080p@80hz maxed, 1440p@60hz at lower settings; RX580 better in newer games
>GTX 1070 - 1080p@130hz /1440p@60hz at high
>GTX 1080 - 1080p@144hz / 1440p@60hz maxed, 4k@60hz in a few games; Probably the highest end card you need for 1080p/1440p
>GTX 1080Ti - 1440p@144hz and 4k@60hz maxed/high in many games
RAM:
>Check your Mobo QVL before buying any RAM
>Ryzen CPUs benefits a lot from high speed RAM
General:
ALWAYS LOOK AT PRODUCT REVIEWS!
Always consider an SSD. Try buying a large SSD for what you'd pay for your SSD+HDD combined, and add a HDD later
NVMe SSDs aren't for a faster OS boot, they're for productivity/scratch disk/VMs. NVMe and M.2 are not the same thing, M.2 is a form factor.
The Ryzen lineup comes with surprisingly good stock coolers. consider using them over any