I had (? have!) a lot of trouble keeping track of what I can do at various points of the game with the new level system. It's likely you will come across at least one thing that you'd like to do, but can't, because of the level system. Earlier Tales had much simpler requirements: to participate in a test, you needed to pass the Initiation of that Discipline. To get a skill, it usually needed some tuition (if you were getting it from a School) and/or prerequisites.
In Tale 3, however, this has gotten a lot more complicated. There are now levels that are attainable via passing Tests (and their, usually easier, associated Principle) along with the Initiation to a Discipline. Every Initiation, Test and Principle passage grants you a level, which then unlocks further content (either skills or Tests.)
Hopefully, this little guide will ease the burden of trying to find out "What can I do when??"
Just entering the game - Level 0
School of Architecture
School of Art and Music
Level 1
School of Architecture
School of Harmony
School of the Human Body
Level 2
School of Architecture
Level 3
School of Architecture
School of the Human Body
Level 4
Level 5
Level 6
School of Architecture
School of the Human Body
Level 7
School of Harmony
- Navigation - First degree (of 6?) - very important
School of the Human Body
Level 8
Level 9
Level 10
School of Harmony
Level 11
Level 12
School of the Human Body