You're literally going to be starting from scratch...
[Add a new case to the list as well if you want front usb 3.0.]
PCPartPicker Part List
CPU: AMD Ryzen 5 2400G 3.6 GHz Quad-Core Processor ($167.99 @ Vuugo)
Motherboard: Gigabyte B450M DS3H Micro ATX AM4 Motherboard ($99.99 @ Amazon Canada)
Memory: Team T-FORCE VULCAN Z 16 GB (2 x 8 GB) DDR4-3000 Memory ($92.99 @ Newegg Canada)
Case: Cooler Master MasterBox Q300L MicroATX Mini Tower Case ($54.99 @ Amazon Canada)
Power Supply: Corsair CXM 550 W 80+ Bronze Certified Semi-modular ATX Power Supply ($59.99 @ Canada Computers)
Total: $475.95
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2019-08-24 22:12 EDT-0400
[Get by on the 2400g's igpu until you can afford a new gpu.]
I tried to come up with combinations for a Ryzen 2600, but they all go over budget when trying to include a gpu:
PCPartPicker Part List
CPU: AMD Ryzen 5 2600 3.4 GHz 6-Core Processor ($181.50 @ shopRBC)
Motherboard: ASRock B450M PRO4 Micro ATX AM4 Motherboard ($83.95 @ Vuugo)
Memory: Team Vulcan 8 GB (2 x 4 GB) DDR4-3000 Memory ($56.99 @ Newegg Canada)
Video Card: Gigabyte Radeon RX 570 4 GB Gaming 4G Video Card ($159.00 @ Canada Computers)
Power Supply: Corsair CXM 550 W 80+ Bronze Certified Semi-modular ATX Power Supply ($59.99 @ Canada Computers)
Total: $541.43
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2019-08-24 22:24 EDT-0400
[This build has no new case, 8GBs of ram(you will want 16GBs at some point), and an Rx 570 4GB model(the best gpu for budget builds, as far as retail prices go.).]