There are 4 different tournament difficulty levels. The tournament level you can enter is determined by your Weekly League division.
You can also enter any tournament level below your Weekly League division.

Rookie - Weekly League Division - Rookie I, II & III
Professional - Weekly League Division - Professional I, II & III
Expert - Weekly League Division - Expert I, II , & III
Master - Weekly League Division - Master I , II & III

The biggest prizes can be found in the Master level. So earning promotion in the Weekly League is the key to winning big!