Should I Start My Digital Marketing With Email Marketing Or Social Media Marketing?

I have a small company which provides academic writing services and the dissertation help UK to the students who suffers to write their own assignment. I never did any marketing of my business, but due to the recent competitions I am facing, I have decided to turn the table over by aggressive marketing of my business. Being a new in the marketing world, I need some sincere suggestions regarding the email marketing and the social media marketing so I can choose it for my marketing.

I have been in contact with a digital agency in recent times, and they have recommended me to use both for my marketing. But I think they were recommended it because of their own personal interest and not considering the needs of my business. Being in the writing business for more than two years now I know what things attract the students and how they like to get approached by the writing companies.

I have just some questions regarding the effects of using such mediums for approaching my clients. However, the only answer I am getting from that digital agency is that leave it to us, and we will show you the power of digital marketing.