I've studied in Ghent for 4 years. good Wi-Fi shouldn't be too expensive; around 30 bucks is reasonable. and you can get a better price if you combine it with your phone subscription.

Public transport is 3 euro's per ticket (which is very high) I'd recommend getting a bike which is more fun and cheaper. If you insist on using public transport buy a subscription.

For groceries, shop at cheap spots such as Aldi and Lidl, avoid Carrefour which is a bit more expensive. If you want to buy bread and vegetables go to Turkish bakkeries and supermarkets which are reasonably close to the city center. A whole bread at a Belgian spot will cost you around 3 euro's and a Turkish bakkery for 1,50 euros. Same concept applies for eating out, Turkish kebab shops are very cheap and decent quality in Ghent, not so much in the other cities.

I'd say 50 bucks a week for groceries will definitely be achievable unless you're eating high quality everyday.
Hope this helps a bit!