I'd probably just ensure the Laptop he buys can be upgraded. Often they can't...though generally it will only be the RAM (Random Access Memory) that can be added to anyway.
Additional RAM will aid in both the speed the machine can operate at as it stores data on the fly so to speak, and saves the computer searching the hard drive constantly for information.
Usually the more RAM the PC has the more complex the games it can handle.
The actual speed the computer runs at will probably not be able to be changed, that is governed by the actual size / speed of the Processor fitted, which will be mated to the Motherboard.
So the faster the Processor the better for gaming...but, the faster the Processor the more you will pay.
