This answer applies to undergraduate / bachelor degree students.

There is no set number of Level 1 units you must complete before enrolling in Level 2 and Level 3 units.

You can enrol in an undergraduate unit (Level 1, Level 2 or Level 3) if you meet its prerequisites. Search the Unit Details section in UWA Handbooks for information on unit prerequisites. For example: The unit CLAN2001 The Golden Age of Athens has the prerequisite "any Level 1 CLAN unit".

It is recommended that you enrol in only Level 1 units in your first semester of study, regardless of unit prerequisites.