CPU : R5 1600 | $210 link
Mobo : MSI B350M Gaming Pro | $80 link
RAM : Corsair Vengeance LPX 16GB (2X8GB) 3000MHz | $127 (Ryzen is memory speed sensitve) link
Power Supply Unit : EVGA 650 G1 | $80 link
Case : Corsair Carbide 270R | $70 link
SSD : Samsung 960 EVO 256GB | $128 link
HDD : WD Blue 1TB | $50 link
Graphics card : Gigabyte GTX 1080Ti Gaming OC | $700 link
This should come to around $1500 USD (Without the OS, Either get a OEM key, Linux or pirate Windows)
The R5 1600 has six cores and comes with a cooler that will allow it to overclock a bit.
The case is nice (if you want a better looking case I recommend going for a case with tempered glass).
You can get the price down a bit more by shopping around, but this is a good starting point.