There are so many laptops out there it's really hard to tell these days. While I have never regularly used a laptop myself, I did sometimes sell them as part of a computer parts store for folks who wanted a laptop. We custom built towers for folks but just sold pre-built laptops with and customized them and such for the folks. As for brands I always preferred working with the lenovos we had, and tended to recommended them to our customers. But it's probably a matter of preference. More a 'what feels right' than any kind of brand loyalty thing.
I can't really give you a particular make and model I'm afraid but there are a few things to look out for. CPU, RAM, HD/SSD, and GPU are just as important on laptops as they are on towers. I've heard there are some slot in graphics cards you can slot into some laptops these days but I would assume that it would be difficult if not impossible to upgrade those parts later. So what you get yer probably stuck with. Might not be able to easily toss an old graphics card and replace it with a new one in a few years like you can a tower.
If you play a lot of rougelikes (DF, Cataclysm DDA, Hengband and all) you are probably going to want to make sure the keyboard has a numpad. A lot of laptop keyboards don't. You can plug in an external keyboard like you can with a tower if you have to, but that increases the bulk. You may also want to look into a small laptop mouse or something as well. You can't really do any kind of gaming like skyrim on a touchpad. (though I'm sure there's folks that practiced enough to get good.)
Battery life is important if you are not going to be near a power source when gaming. Laptops salesmen will often tell you their battery life, keep in mind that what they tell you will probably be longer than what you would practically get while gaming. Battery life estimates are often given with all the power saving features active. When gaming a good number of those power save features need to be turned off or otherwise disabled. If you expect to be able to plug in at all times you are actively playing and can keep it off or otherwise in low power mode between plugs, battery life is less of a concern.
And this last one is more something I heard of than have any kind of experience with, but I hear good gaming laptops (which you should be able to get with that budget) can get quite hot. You'll probably want to look into a cooling pad of some kind to rest the laptop on when playing. Both to keep the flesh of your legs unmolten, and to help the laptop dissipate heat. Often times laptops (and a lot of towers these days) will throttle their power levels and performance when getting near their temperature redzones. Some kind of supplementary cooling system will again, add some bulk, but help keep the laptop running at max performance and keep your nether bits unmelted.