I believe that 5 sets of 5 reps is what I would think of, start off with low reps, and then once you start getting the hang of it and become stronger go for higher reps. Try one handed push ups here and there a bit for practice. Also when you’re doing a practice one hand push up make sure to have your legs widely spread and keep your core tight. Do 5 sets of 5 reps everyday or every 5 hours until you are able to do a one handed push up.