I understand that I can get paid for 3 study guides per class, but am I required to make 3 study guides per class?

You're only required to make study guides for the exams you have for that course. The maximum number of study guides you can be paid for is 3 per course, per semester.

However, you must have 3 study guides that qualify for payment in at least 1 course in order to qualify for your End-of-Semester Bonus.