There was a short period during my college years when I religiously consumed ginkgo biloba with the hopes that doing so would enhance my memory. I think I did this for several months. I honestly doubt there were any significant effects. I'm not sure, but I think the premise behind the herbal supplement is to help calm you down, thereby allowing you to concentrate better and learn more time-efficiently. But aside from taking the pills, my study habits and routines were the same while I was on them compared to when I wasn't. I did fairly well before and during; there was no improvement, and there was no decline after I stopped. I strongly believe that the best favor you can do for yourself is to just be diligent and to get enough sleep, which I know is rare for college students. In college I averaged about 3-4 hours of sleep per school day (S,M,T,W,R) because I was so obsessive about studying. Maybe ginkgo biloba did help a little, because I think that I would have done just as well if I had not taken the supplements and had only gotten much more sleep. And as we all know, sleep deprivation 'causes physical and mental fatigue, and it prones you to consuming excessive levels of caffeine, which can increase stress levels.
Point is that it wouldn't hurt to try ginkgo biloba. Try it out for a little while, but I don't suggest spending your entire salary on it. You're probably better off just being time-efficient and taking care of yourself with good nutrition and adequate rest.
Good luck,
Marcus