What growth techniques would you recommend for this?

Hey Davide, very cool site concept! I would suggest adding a mailing list sign up form at the bottom. Consider offering people something a gift, like a pdf that highlights all the different moves, in exchange for their email address. When they do sign up, you can start asking them questions about their experience.

I would also recommend measuring analytics on how many times each video is being played. If some way outperform others, it would be interesting to note anything that's unique about it, like the video length, the way it was shot, the difficulty level, etc.

I like the high-level organization of the videos: beginner, intermediate and advanced.

You could take this further by creating a sense of progression for users. I've considered taking salsa lessons and checked out the beginner category but the topics seemed sporadic. Check out Khan Academy for some inspiration. They do a great job at this.

Perhaps a curated playlist could work.

In terms of how to grow it. I think nailing product is more important right now. Finding just enough users to get feedback and observe their behavior. Where do they hang out at? Are these users sticking around? How are they using Vueltaclass?

Trying to grow before it becomes sticky to a core group of users could be like pouring water into a leaky bucket.