ATC is a peculiar job - it matters not one bit if you are a graduate with several degrees, or someone who has just scraped in. Usually young people stand a better chance at busy units, but plenty of "oldies" can also validate. Some people can do the job; others cannot. Unfortunately not all the "cannot" people can be weeded out during initial training. I've seen plenty of trainees who have come through the college with flying colours and got no furtehr than the simulator at their unit.
I can't offer advice on college work - that's the job of your instructors. But, once you get a posting read all you can about the place in the AIP and get some maps out so you are familiar with lcal geography, etc. That may well help..