I'll echo ReductiMat, if you are able to spend a lot of time in Whistler, that is by far the best/safest/easiest way to progress in jumping. I got back into mountain biking a few years ago at 35 (used to ride as a kid but never much of a jumper). Within a year I bought a DH bike and started riding at Whistler a lot. I took a few weekend camps which they don't seem to run anymore unfortunately, where you had the same coach for two full days. One of those years me and the other guys in the group just said we wanted to be able to clear A-line so we spent the entire weekend working up to it, first dialing in technique then just lapping either following the coach or he would follow and watch us. It made such a difference...
A-Line was as far as I got, even then I never cleared the left side jump after the rock drop, and I _barely_ backsided the GLC jump and moon booter. It was just volume of riding and slowly progressing when feeling good and getting comfortable with the speed that did it for me. I've never actually crashed on a jump trail (knock on wood) although I had a few scary nose dives over the years.
Funnily enough, the last 3 summers I've only done a handful of park days (young kid, sold DH bike) I've regressed and struggle to clear the bigger stuff on A-Line now. I just don't ride jumps that size/speed trail riding cuz I ride solo often and don't want to risk injury in the woods (bike park is different w/ professional medical staff).
I also agree if you clear C-more easily you are ready for A-Line.