Teenager wanting financial advice prior to 18th

Hello! I am turning 18 soon, and I want to start on the right foot financially.

I'm in Canada, and I'm planning on maxing out my TFSA with 7000 the day I turn 18, money I've saved throughout highschool. I'm working throughout the summer and (based on my current spending habits) I should have about 9 grand more at the end of the summer, should I invest this additionally else where, or wait until next January and max out my TFSA once again?

With the money I have left over that I cannot put into a TFSA (maxed out), should I get a interest building savings account, or will it just not be worth it with the fees?

I am going to university and planning to go to medical school, but my parents are paying for my schooling, at least for all of undergrad, so student loans aren't an issue yet.

For credit cards, should I get one, spend like a debit card, and pay it off at the end of each month? I'm not well versed in this universe but I do want to be competent financially. If you have any ideas, things you'd like to tell me, discouragements etc, it's all welcome.

Sorry if anything isn't clear, I don't know much about all of this.