Of the new cards, an Nvidia GTX 1050 TI or AMD RX 470 is probably the most you'd want to look at. The 1050 Ti would probably be the safest choice, in so far as you can get one that does not need a 6 pin pci-express connector. The 470 might prove useful in games which require GPU power more than CPU power. This is for 1080p gaming, if you're gaming at lower resolution than that you could probably get by with a 1050.