Ranks are earned from experience, which is based on performance of each playthrough. 

0. Unqualified     (less than 0 exp)
1. Beginner     (0 - 999 exp)
2. Novice     (1000 - 1999 exp)
3. Amateur     (2000 - 4999 exp)
4. Professional     (5000 - 9999 exp)
5. Expert     (10,000 - 49,000 exp)
6. Master     (50,000 - 249,999 exp)
7. Legend     (250,000 - 499,999 exp)
8. Wizard     (greater than 500,000 exp)