I cantered on about my 5th or 6th lesson? A really awful instructor parked one of her horses at one end of the arena, then put me on a very herd bound horse at the other end and smacked him on the butt. Well, I cantered alright, my horse literally crashed into the other....I was stupid enough to stick around, so she then put me on another horse, told me to hang on, smacked it on the butt, it took off at a nice fast canter, the saddle slipped (she'd saddled it!) and I ended up on the horses side. I was smart enough to call it quits after that!
Found a real trainer and she had me canter on the lunge line on my 3rd lesson with her I think? Only for a minute or so, she just wanted me to get over my fear of it thanks to the few wild rides I'd been on!
My lil kiddo was cantering on her 4th lesson or so. The kid has incredible balance and absolutely no fear. She was riding a 16hh warmblood with absolutely no issues at a posting and a sitting trot and in 2 point so my trainer put her on a lil pony and she was able to canter without a problem.