Dell Inspiron 5721 - Graphics Card Installation/Improvement

Hello, I'm looking to install a new graphics card into my laptop - a Dell Inspiron 5721. It was a gift to me, and I use it for gaming as well as school/office-related purposes.

I don't know a large amount about this computer specifically, all I know is that I need a better graphics card besides the stock card that is installed (I do not have the model with the AMD Radeon). 

If anyone could point me towards a good product to purchase, or simply where to look, that would be great!