I myself find doing Magic Theory every day as being the best for getting knowledge. Usually gives 1 every time. While you can make up for your other stats if you focus on studying with other classes. I myself don't suggest dueling practise or the other classes which give multiple points, as them giving you some aren't guaranteed. I found grinding knowledge makes the exam a breeze and the trial of mind too (especially if animal form is bought), where other stats can be focused on at the expense of knowledge. But that's just how I went with it