I have a large (24x10ft) terrace on 7th floor of a condo in the Yonge/Eglinton area, it faces north but I get a couple of hours (midsummer) of sun from the east and then from about 12.00 to 6.00 p.m. from the west. It can also be windy, so which plants would be best, perennial if possible, cheaper than annuals every year, although I don’t mind get some of those. I also have a small balcony which faces west.
You are fortunate to have such a lovely terrace!
Container gardening is lots of fun and there are many plant choices available for sun and shade, even in a windy location such as yours.
Container selection: Avoid ceramic and metal containers, as ceramic will crack over winter due to the absorption of moisture and the freeze/thaw cycles of our winter climate. Metal containers can rust, and absorb heat which is detrimental to plant roots. The best containers for terraces/balconies are either the fibrestone or polyresin double-walled, which offer some protection for over-wintering. If you choose single-walled fibrestone, they should be insulated with 1/2″ styrofoam inside. https://www.torontomastergardeners.ca/askagardener/insulating-plant-containers-on-a-balcony/
Both types should provide positive drainage with either drainage holes in the bottom, or large gravel with a layer of landscape fabric between the gravel and soil to prevent plugging of air space between the gravel.
Container size: The bigger the better. The more soil you have in a container, the more likely the plant is to survive the winter. NOTE: If you are in a condo, always check with the Condominium Association by-laws to ensure you are able to install a larger planter size. There may be some restrictions such as weight capacity and drainage concerns.
Soil: Use a good quality potting soil or vegetable/agromix soil (if you wish to plant herbs and edibles). I like to add soil sponge to my planters, as it helps maintain soil moisture, especially in windy areas where soil is likely to dry out faster than at ground level.
Plant Selection: Plant according to your container size and hardiness zone (it will be a zone lower on the 7th floor). It is possible to over-winter perennials and some smaller nursery stock, however (see above) the freeze/thaw cycle of our winters can be quite destructive to roots. Wind can also dessicate leaves and any other exposed part of the plant. In that respect, perennials are a good choice as they die back in the winter.
You can plant any perennial that you would plant in a garden so long as you follow the sun/shade, moisture and hardiness considerations. I would suggest the “tried & true”, such as Hosta, Astilbe, Ferns (or tropical ferns Boston, Kimberly Queen), Heuchera, even some perennial grasses such as Japanese Bloodgrass and Forest Grass. Tropical plants (not hardy) such as Alocasia, Philodendron, Palms, depending on space as these may tend to grow a bit large, add a real lush feel to a terrace. And herbs can be added in small containers for fragrance and culinary purposes.
The Toronto Master Gardeners do presentations through the Toronto Public Libraries, which includes Balcony Gardening. I would also recommend you check their website for upcoming engagements.
Have fun with your terrace gardening!