Perhaps look at starting with something like this:
CPU: AMD - Ryzen 5 2600 3.4 GHz 6-Core Processor ($164.89 @ OutletPC)
Motherboard: Gigabyte - B450 AORUS M Micro ATX AM4 Motherboard ($89.84 @ Newegg)
Memory: Team - Vulcan 8 GB (2 x 4 GB) DDR4-3000 Memory ($55.88 @ OutletPC)
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2019-03-26 08:02 EDT-0400
Then upgrading the GPU down the line. If the RAM you have is 2666 or faster then ignore that from this list.