PCPartPicker Part List:
https://pcpartpicker.com/list/jvTdpG
CPU: AMD - Ryzen 5 3600 3.6 GHz 6-Core Processor ($199.00 @ Amazon)
Motherboard: ASRock - B450 Pro4 ATX AM4 Motherboard ($64.99 @ Newegg)
Memory: Corsair - Vengeance LPX 16 GB (2 x 8 GB) DDR4-3200 Memory ($77.99 @ Amazon)
Storage: Crucial - MX500 500 GB 2.5" Solid State Drive ($59.99 @ Adorama)
Power Supply: SeaSonic - FOCUS Plus Gold 550 W 80+ Gold Certified Fully Modular ATX Power Supply ($51.98 @ Newegg)
Total: $453.95
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2019-07-18 18:04 EDT-0400
I didn't include a Case or Operating system. And one issue may be running a Ryzen 3000 on a B450 motherboard due to BIOS incompatibility. There are updates but you need an older Ryzen chip to do it or use
https://www.amd.com/en/support/kb/faq/pa-100 to get a loaner. You could also save some money and get a Ryzen 2600/2600X which will work no problem, and be about 50 bucks cheaper but not as good for gaming.