An extarnal gpu is about all you can do, the only problem is its not plausible. The slot is a good 100-250 dollars plus you need an external gpu and a desktop psu to run it. Some people have done this for macs but that was with a 750 dollar external PCI e slot. So in general you are going to be better off on using a desktop for gaming, or a laptop with better integrated for games. You wont be able to run high or anything but it will be playable.