cheapest - best-bang-4-bucks is the RX 570 4G = 130$ for a good one
1650 6G is also nice - but for that price you can consider a Vega 56 - or you wait and see what NAVI brings
PC: R7 2700X @PBO + RX 580 4G (1500MHz/2000MHz CL16) + 32G DDR4-3200CL14 + 144hz 1ms FS P + 75hz 1ms FS
Laptop: R5 2500U @30W + RX 560X (1400MHz/1500MHz) + 16G DDR4-2400CL16 + 120Hz 3ms FS