Avril Lavigne finally ... in an oversized black shirt dress with graffiti-style writing on it. She paired the outfit with fishnet tights and black lace-up combat boots, plus a red electric guitar ...

Lavigne and ... "Tyga and Avril are getting to know each other," a source told PEOPLE earlier this week. "It's very new. It's very casual." Never miss a story — sign up for PEOPLE's free daily ...