The "best" screen in that price range is definitely going to depend on what you want. You could get a decent 4k gaming monitor in that price range (link included) but 4k with that card will see a lot of frame drops vs 1080p or 1440p. If you really don't know what you want then you just need to look at what people typically decide on when buying a monitor
1. Size (there are monitors about 50", but I honestly don't enjoy anything bigger than 27-28 because I have to be so far away from the screen)
2. Resolution (you know, 1080p, 1440p, 4k)
3. Response (1-2ms works great for pretty much anyone who isn't an MLG, but some people would disagree)
4. Refresh Rate (at your price range anything less than 60 Hz is NOT a good buy)...