As usual, the answer is “it depends”. In the context of gymnastic inspired training, and to keep things simple, I’d suggest the following as a rule of thumb. If you can’t perform 3 reps with a good form, the exercise is too difficult, if you can perform more than 8 reps with a good form, the exercise is too easy. Aiming for the ability to perform 5 sets of 5 reps would be a good place to start.
