Ok. Toronto is not the coldest city (Winnipeg, Regina and Saskatoon are colder), but it can get very humid during winter because it's right by Lake Ontario, so prepare for winters that will have frequent snowfall (unlike Winnipeg, Regina and Saskatoon).
If your jacket doesn't have a hood, I suggest wearing a hoodie underneath and sticking the hood outside of the jacket so that you can cover your head. In addition, always wear a toque (also known as beanie or winter hat) and gloves. For your first few days you can survive with whatever toques and gloves you can find in your home country, and once you've been in Toronto for a couple of weeks, decide whether you need a lined toque and/or waterproof gloves, or if you're fine with what you have. When it snows and/or the environment is very humid, try to layer up as much as you can under your jacket. For example, you can wear a t-shirt, then a long-sleeve shirt on top, then your hoodie and then your jacket. Another option is a t-shirt or regular shirt, then a warm wool or cotton sweater, then the hoodie, then the jacket. Bring a scarf - any scarf - and wear it well wrapped around your neck.
As time goes by, you will see how you feel in the weather, and can start buying things depending on your needs: perhaps some microfleece sweaters or sweatshirts to wear as an additional thin layer, or thermal underwear to wear under everything else, or simply a heavy duty winter jacket. Like I said above, you will find out if regular knitted gloves and hats will do, or if you need a thicker lined hat and/or leather or waterproof gloves or mittens. You will also see if you're fine just wearing regular jeans and pants or if you will need thermal underwear underneath. In general Toronto is not too bad, but excessively humid days can be a bit too much.
