Perreado comes from the verb perrear, which literally means "to dog" or "to dance perreo." However, in this context, it's used colloquially to mean "to work hard," "to hustle," or "to put in a lot of effort."
In the song, the lyrics "sin saber que le he perreado" (without knowing that I've hustled for it) highlight the speaker's dedication and the immense effort he's put into achieving his success, contrasting it with those who think he got everything easily. It's an interesting example of how Spanish slang can evolve and take on new meanings.
"Paso a Paso" ("Step by Step") is Calibre 50 answering the people talking behind their back. It opens with the singer relaxed with a cigarette, focused on his own business, and unbothered by what anyone says.
Most of the song pushes back on a familiar complaint: that success changed him, that he got lucky, that he did not earn what he has. He answers it the same way every time, pointing to the work nobody saw and reminding everyone that no one helped him carry the load.
The song also carries a thank-you to the group's fans, promising to keep moving forward one step at a time, no matter who criticizes him along the way.