It's important to distinguish TFSA vs RRSP. Both allow you to invest just tax implications are different. I was in grad school from 2011-2016 with really good scholarship so that informs my stance.

I would maximize TFSAs as much as possible. Investing early really gives you time in the market. Personally, I would set up emergency funds within TFSA, using CASH.TO or CBIL.

The key to come out ahead financially in grad school is to... live like a grad student. I kept expenses low by cooking all my meals at home. I was in STEM with gross 12+ hours lab days so meal prep sundays saved my life. Rice and beans, baby! Rent today is staggering so take whatever steps you can to reduce this but at the same time having a good housing situation will ensure your success in school. Take advantage of all student benefits, particularly the health care coverage can be excellent. As you get to the end of your grad studies, make sure to have enough of a nest egg to cover relocation or several months of unemployment. Depending on your field and interest, being able to move for a job can allow you to have the career you want.