Depends on what and how much are you going to store in it.
If it's only college stuff then 500gb will be more than enough, you will still have a lot of space left even after a year.
But if you will be using it for other purposes too, like gaming, watching movies, videos, images, etc. then a 1 tb - 750 gb hdd should be the least.
And 8 gb is recomended (depends on what you do). 6-8 gb can work.