Those are the first things you need to buy after you rent an appartment:
1- A Mattress to sleep on
There are standard dimensions for Mattresses,
Twin : 39 x 76 inches ( 99.1 x 193 cm)
Twin X-Long : 39 x 80 inches (99.1 x 203.2 cm)
Full : 54 x 75 inches (137.2 x 190.5 cm)
Queen : 60 x 80 inches (152.4 x 203.2 cm)
King : 78 x 80 inches (198.1 x 203.2 cm)
Cal-King : 72 x 84 inches (182.9 x 213.4 cm)
If you are single, living in a 1 1/2 apartment, I recommend you to not get king or queen because they take too much space and will make you feel the place too small.
2- Eating stuff, spoon, plates…
These things you can get from Dollarama
3- Kitchen stuff, table and a chaire
Get them from canadian tire / wallmart