Welcome. I am in Toronto.
The most convenient place to shoot is Calibre Shooting Club (previously Grange) which is located at Target Sports in Gormley. The location is just off the 404 highway, so it's convenient, though traffic on weekdays is still enough to discourage a casual trip to the range. Membership is very expensive, maybe the most expensive of any club in Canada, at about $600 or so. It's indoors, so if you want to shoot anything other than handgun, it's not that great. But for handgun I think it's a good club. Most of the facilities have been upgraded recently, there's a very nice store there, and active IPSC and IDPA groups.
North of Toronto Barrie is a very good club. Guelph is good too, but the distance is problematic. I don't know much about the Alliston club.
There is an Oshawa gun club with some excellent facilities, but I don't think they are handgun friendly. There is also a Marksman club in Oshawa that I know nothing about except that it's indoors and 25 M.
There is a Toronto Revolver Club, but it seems to be a very secretive and closed organization. No knowledge of it.
