Which ram for this laptop

As i would recommend right now is that you should look for ram stick with an 2 pair ( 2 exact same ram stick to be more simplefied ).
your laptop also supports 1600mhz ram speed, that way there is no reason to stick to lower ram speed, unless you budget comes in play.
Further on, remember to search for ram cards with an SODIMM form factor. these cards are build for laptop and an DIMM ram card are build for desktops/servers.
Ignore ECC and buffered ram sticks as it is an waste of money. your laptop doesn't support it anyway.
The maximum ram capacity is 16GB, but that doesn't mean you should get 16GB ram sticks. and then obviously i mean 2x8GB ram.
As for your operating system. check if it an 32x or an 64x operation windows 8 system (or if you upgraded to windows 10). 32x operating systems only support up to 4GB of ram.
If you are purely using it for gaming and doing nothing else with it. 8GB is the sweet spot here.
Unless you want to do some little workstation work like video editing, photoshop, programming. or having some application open while gaming. 12 or 16GB is then your best choice.
So the following options might be good for your laptop.

Option 1) buy 2x4gb ddr3 pc3-12800. this is for if you are using it for gaming and nothing else is open.
Option 2) buy 2x6gb ddr3 pc3-12800. this is for if you are using it for gaming and having programs open in the background. maybe like skype. chrome tabs or something else small.
Option 3) buy 2x8gb ddr3 pc-12800. this is for if you are using it for gaming, workstation work and everything else that requires lots of ram. this option might be not nessesarly for you, but if it does, then it might be the right option.

and not saying that your options are bad, it is fine tho. but if you are planning to upgrade your laptop, then it might be handy if you benefit yourself with a bit more ram storage. the performance might not be significant, but when you are running multiple application, then you will notice an improvement and especially when doing workstation work as descripted above.

conclusion: this is the ram i reccomend you for your laptop (G.Skill S Q F3-12800CL9D-8GBSQ)

great job if you made it this far xD