"I wrote a fairly good content 10 days ago, took me 3 hours of research and writing plus review and linking in facebook and twitter. I had almost 100 views and 10 upvotes, made 50 cents.
Two days after that, as a test, I postes a youtube video of a song that I like, absolutly no maketing or anything involved and got 15 views and 1 dólar reward."

I think, unfortunately, you have effectively summarized why many of us have felt Social Media is fucking stupid for a very long time. This exact same stuff regularly happens to me, or I release two very similar-in-quality posts and one makes 7 cents while another makes $300. Unfortunately, as I believe it says in the white paper, Steemit is kind of a lottery. You aren't rewarded on a fair, regular basis (unless you buy a ton of stake to reward yourself). All you can do is release the best content and hope for the best.

You can release garbage content, and because you get more "lottery tickets" that way, the chance of someone with some stake seeing it is higher. However, that is a short-term strategy that doesn't create followers.

The only long-term-guaranteed strategy is blood, sweat and tears. I have been writing for decades and even with a lot of content pre-brainstormed, regular quality production is difficult and often unrewarded.

Steemit isn't a magic money machine...unless we go to the moon and you are Hodl'ing, I guess.