No one: Hanzi reform. Starting using modified Hanyu Pinyin as second official writing system for kids education, for farmers and for imported foreign words. This is so basic and important that all other changes will rely on this one since it will open a door widely for every Chinese. This change is a fundamental and profound one that is going to change Chinese from current poor situation for ever.

No two: Education.

No three: political reform including rebuild of entire legal system.

No four: culture reform including imports all good systems and cultural elements from other countries.

No five: ...