Laptop RAM help

Hello, I have recently purchased a lenovo g50 laptop with an A6 processor, r4 graphics, 1TB hdd, and 4gb of ram. I want to upgrade the ram to increase the performance of the laptop's apu. The max ram for it is 8gb. Do I just buy another 4gb of the same clock speed ram or am I able to buy 4gbx2 of a higher clock speed to get even better performance or is there like a laptop limit to that. I have very little experience with laptops, i'm more of a desktop guy.

Should be fine if you purchase another 4GB 1600MHz stick. Opening up the laptop and see what manufacture made the RAM and just find a similar stick online for best compatibility. You could search the skew number you find on the RAM. 

Also make sure that it actually has another slot. Some will only have one slot so you will need to buy an 8gb stick.

Here is the specs: LINK

There are two RAM slots but, yes, It is a good idea to check whether there is two 2GB sticks or a single 4GB stick. If there is two 2GB stick you will need to buy an 8GB (2x4GB 1600MHz) kit.