When picking a laptop for gaming and university work, video card choice is THE most important factor. Get one of the ones with an upgradable graphics card module (dell and HP make some) and the best graphics you can afford. If you have to skimp on ram at first or other accessories to afford the model with a better video card, it will be well worth it. next most important is processor speed. some processors are upgradeabble these days, but for the most part you will be stuck with whatever you choose there. Ram, HD space, etc, all that is upgradeable.
Screen size is nice, but keep in mind you can always get a bigger external monitor. as a matter of fact, you may even want to get a cheap monitor anyways depending on you area of study. A dual monitor setup does wonders for paper writing and computer codeing.