There is a lot of sex, nudity, substance abuse and swearing. The show uses dark humor and slurs quite often. There is rape. There are heterosexual and homosexual relationships with explicit sex (the latter in not present in the first season). The show is definitely not appropriate for younger teenagers.
At the same time, there are role models. One of the main characters, Fiona, is eighteen and manages to keep her her five sibling afloat by her various, low-income jobs. Ian is hardworking, manages to get into a prestigious military school despite his background, and has to deal with mental illness. Mickey is the most unlikely character to be considered a role model, but he overcomes life-long abuse from his father and wears his sexuality proudly (in later seasons).