You already have one of the best CPUs for that socket and anything up from it wouldnt yeild any worth while performance. If you want something new you will need a new mobo and DDR4 RAM. For a new build something like this
PCPartPicker Part List:
https://pcpartpicker.com/list/tBzGGc
CPU: AMD Ryzen 5 3600 3.6 GHz 6-Core Processor ($174.99 @ B&H)
Motherboard: MSI B450 Gaming Plus MAX ATX AM4 Motherboard ($104.97 @ Amazon)
Memory: G.Skill Ripjaws V Series 8 GB (2 x 4 GB) DDR4-3200 Memory ($46.99 @ Newegg)
Total: $326.95
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2020-02-29 08:19 EST-0500
You could even look for a used Ryzen 1600 or 2600 which should be in the 60-100 USD range and buy a cheap ASRock B450 motherboard which are around 50-70 USD, cheaper if you looked on the used market.