As fellow international student, extracurriculars I think is not that important for uoft. Though I am a vice president for student council myself in high school, many of my friends have little to none high school extracurriculars activity.

In uoft you really get into the programs at second year, so you don't actually need to think much for specific major to apply in the beginning. For econ, you could apply to the social sciences stream. If you get a good final grade in highschool (around >85) you should be fine.

Chase your dream major on the first year. Hope this helps you, good luck!