Barry Feldman is a veteran of online marketing. He's helped thousands of companies develop stronger brands and more effective communications with services including content marketing consulting, conversion copywriting and social media.
You start with a website, which is the hub of all your online marketing. Even if you have a website, chances are great, if you're new to online marketing much has to be revisited.
Yes, you'll proceed into email, social, search and so forth, but the purpose of each will be to drive qualified traffic to your site, so it must be ready to do business.
At my site, you'll find a free guide to creating a marketing focused site, "21 Pointers to Sharpen Your Site."