Resolution: Never get anything less than a 1920 x 1080 display. It’s rare to find one with a lesser resolution, but if you do, run. If you have a GTX 1070 or GTX 1080, you may want to consider a 2560 x 1440 display. 4K (3840 x 2160) screens are an option on some gaming laptop, but it’s rare you’ll be able to both get enough graphical fidelity at that resolution while also maintaining a smooth frame rate.
Cheaper gaming systems today are equipped with lower-tier cards like the Nvidia GeForce GTX 1050, GTX 1050 Ti, or GTX 1060, but these modern budget cards are surprisingly effective. You'll be able to play smoothly in HD, just not at the very highest settings in newer games. These may be budget systems, but this generation of entry-level graphics chips is fairly capable, so don't be too worried that you won't be able to play most games moderately well. Virtual-reality gaming may be a stretch in this price range, but the GTX 1060 is the least expensive VR-capable card, so some laptops at the higher end of this price range will (just) get you in the door.
Gaming laptops can put a serious dent in your wallet, with some of the fancier models costing upward of $3,000. But who says that the right rig has to cost an arm, a leg and the soul of your firstborn? Fortunately for the fiscally conscious gamer, there are some sub-$1,000 notebooks that can run graphically taxing games like Destiny 2 and Shadow of the Tomb Raider at solid frame rates.