Good command of Italian is needed to understand this lecture. If you have problems understanding this video welcome to the Scuola di canto, where the teacher Elvira Tkachenko, a student of these Italian singers, will explain everything in detail.
It is very difficult to name a universal learning algorithm that would be suitable for all types of voices. Because there are a lot of timbres and types of voices a repertoire must be selected individually.
We always select a repertoire in one of the first lessons after determining the vocal timbre, the degree of the student's preparation, and the willingness to learn.