I am also s second semester Ph.D. Business student from the U.S. and I'm working on digital marketing - more narrowly focused - as a central Research Objective. My advice is to define your central Research Objective you think you want to explore for your dissertation now (it can evolve), read a number of literature reviews, outline the topic you want to explore and then write a literature review. Ideally this should be integrated into your coursework for a central area of focus. Hope this helps.