I don't have any experience with this kind of exercise, but from the looks of it I'd say the challenge is threefold:
Climbing the rope / pulling yourself up on the rope. You could practice this with regular pullups and chinups on a bar, of just climb the rope up and down while trying to use your legs as little as possible.
Moving your lower body around in space. This is mainly a core / legs exercise, so you could do stuff like hanging leg raises (again starting on a bar).
Doing the exercise while hanging from a rope. I think the best way to work on the necessary coordination and balance is just doing the movements on the rope. So after you're worked on your strength, you should move back to the rope ASAP.
Hopefully this is of any use to you. Good luck!
Edit: I'd aim for 10-12 reps per exercise. Lower rep ranges are generally intended for hypertrophy exercises (lifting weights to get bigger). The stuff I mentioned above should be fine.
I tried last night to do toes to bar like you mention. I'm weak on the last 60 deg of the pike movement. I can cheat by using my shoulders to lean back (front lever type movement), but this puts a lot of strain on my upper back (not injury type strain, just in weak).
Straddle V-hang pullups are also a bit weak. Can't do close leg V-hang pullups yet.
Basically just need to get my pike/toes to bar stronger and work on front lever I guess.