Level 121+:
Level 123+:
Level 145+:
Before 150:
Level 150+:
Level 180:
Note: While obtaining the 180 marks at 180 may seem good, saving them until level 225+ will allow you to bypass most of the fourth class leveling.
Additional easy marks which you may try:
Additional hard marks you may try:
Additional rare chance marks you may try:
Marks which will no longer be available to you after third class:
Secrets (level 150). Spheniscomancy (level 180)