my first gaming laptop had a GTX560M, i5 proc, 8GB ram, 15inch Full HD, MSI brand (umm around 4 years ago I think, SRP was around 50K). after about a year, it was replaced by a Asus G75VW (120hz, i7, 16GB ram, GTX670M, 2 750GB HDD, 17inch full HD, bluray drive, SRP around 100k)
both laptops performed well on all the games at that time so these days a GTX960M should be enough for most games. one of the reasons kung bakit mahal yung Asus was the 120hz (that means up to 120FPS which is important in some games). the resolution is also important, most 15inch laptops will only have a resolution of 1366x768 even the gaming ones so if you want full HD, you should check the resolution first since very few 15inch laptops will have full hd resolution
as for RAM, the minimum for gaming should 8GB dedicated (this is important to stress since some laptop graphic cards, even the discreet ones, will still get some memory from the RAM). also, take note that most gaming laptops are not designed for on the go performance, they are mostly designed as desktop replacement - meaning they are heavy and battery life is about an hour only. If you want, you can go for those laptops that have nvidia optimus technology - they have both discreet graphics and onboard, you can switch graphics card as needed, which will result in longer battery life BUT these laptops are typically not built for gaming so the specs aren't going to be as good
lastly, for gaming laptops, the known brands are MSI, ASUS. HP and dell aren't known much for their gaming laptops (in fact, specs wise, their gaming laptops pale in comparison to ASUS ROG ones)
PS
sometime last year, I decided to sell the laptop since I realized it was more of a hassle if a laptop has problems compared to a desktop. pag laptop nasira, buong laptop hindi mo magagamit until maayos yung isang part (and usually it takes time for parts to arrive) pag desktop ang nasira you can easily take out the component with a problem and replace it. so if you're not going to be on the go and will be using the laptop as a desktop replacement, desktop will still be the better choice