There are plenty of grocery stores around Kowloon Tong and City University, here are a few that standout.
TASTE (Festival Walk)
Pro's: Lots of familiar western products, good bakery, good place to purchase "housewares". "Taste" is in the same Mall (Festival Walk) as the MTR train station, so it's very convenient to stop in after a day out when you are returning to residence.
Con's: More expensive than other groceries, generally busier.
If you are looking for western products you'd see back in North America, then "Taste" at Festival Walk is the best option. They carry some similar products and brands that you'd see at a normal grocery in Canada. While I didn't do my grocery shopping at Taste, I did buy laundry detergent, facecloths, and soap at Taste.
Vanguard (Chak On Estate)
Vanguard is personally my favourite grocery store near City University!
Pro's: Large selection, less expensive than "Taste", good soups, snacks, fruit, cheap drinks and kitchenware. After shopping, it is an easy (downhill) walk to the student residences.
Vanguard, at least to me, seems like a more authentic experience, common Hong Kong people shop there, and it is right in the middle of a local housing estate, so it's neat to see locals going about their everyday activities
Con's: No one really speaks English so if you are looking for something you can't find, it may be a struggle. Despite this, I found the staff at Vanguard super friendly and welcoming.
The store is located in the Chak On Estate about a 10 minute walk from the CityU Residences.
It is open from 8:00am to 9:00pm every day.
Map to Vanguard from City U Residences.
Wellcome (Shek Kip Mei)
Pro's: Probably the cheapest option (similar price range to Vanguard), large selection of snacks and drinks, have quite a lot of sales.
Con's: It is the furthest of the three from CityU Residences. It is located in Shek Kip Mei (about a 15 minute walk from Campus). When returning, it is a steep uphill walk carrying groceries.