The dedicated graphics card drains out plenty of battery power. If you are always on the move, consider investing on a 6 cells lithium-ion battery that can last at least 5 hours.
A gaming laptop is generally more expensive than a normal laptop. You can't really find a cheap gaming laptop with all the high end parts. If you are willing to compromise on the CPU speed, you could be able to get one that is more affordable. As a gauge, a acer x27 gaming laptop generally cost at least $300 - $500 more than a normal laptop.
A down side for a gaming laptop is the huge amount of heat it generated. If left without control, it can shorten the laptop lifespan. A good solution is to use a cooling pad to dissipate the heat away. A cooling pad is a pad with three inbuilt 60mm cooling fans placed at the base of the laptop.
The quality of the sound and audio contribute to the gaming experience. The sad part is that most laptops are not able to provide great quality audio system (due to space constrain and size limitation). As such, you might want to get an external speaker.