Digital Marketing is too big and if you are interested in it then try do select you career path in it.
what are your interests? what's your background? have you had any experience at all in digital marketing? it's a big and changing field, so you're going to have to ask yourself some questions, before you really strike upon what it is you want to do.
its all depends on your intrest... if you are crazy about internet and social media and eager to learn new things..if you have a creative mind and strategy to promote business ..then you can choose DM