I run the game just fine with an RX 580 8gb GPU and get 45-60fps in most places on the game. (Ryzen 5 2600, 16gb 2666mhz, 2x2Tb HDDs. 1x500Gb SSD, 5 PWM Case Fans, 750w Silver Thermaltake PSU)
I suggest you look to your power supply for your problem. You should have at least a 750w PSU for your setup.