Your description is not quite correct. Walter White is not a amateur dealer, he is a chemistry teacher who gets diagnosed with cancer. To provide for his family (with the handicapped son) after his death he begins to make money by producing Crystal Meth. And by God, does he make money...
The series shows how a "average" citizen gets dragged into the abyss of organized crime, basically without evil intentions and with relateable reasons. One of the best series ever.