I like function over form. The name, class, and level should be large enough and easy enough to read to sort them fast. The text can be shorthand to keep the font large enough and more direct to the point (I have the book if I need to look it up, right).
There could be a color-coded border for class or even level. I would not want a color background since the printer cost would go up and eyes are getting too old to want to read black text on red background. Using the border for level of the spell might work since I already know the class and would tend to only have those cards in front of me.