Wouldn’t know what the “best” place is and it depends on what sort of fish you want to catch. All the beaches from birdlings flat and further south are good. Some are better than others and some seem to have more of a certain species than others but all pretty much the same. I’d say easiest fish to catch along these beaches other than dogfish is rig if you can get some crabs or prawns for bait. I haven’t come back without catching a rig every time I’ve been to wakanui beach this season.
I think there’s quite a few different fishing clubs in christchurch with a surfcasting section.