I would say, above everything else, if you are trying to rank well for a specific keyword, your website must almost "be that keyword" - make sure the content is really something new, best in your niche so that people will share it and link to it. Sure, social media, blogs etc. - but have you considered creating videos and posting them on youtube?
I would be careful with article submissions - Google is now very clear that all link building needs to be done with intent of getting real visits through the links you build - so your articles must be read by people and motivate them to click on your website. If you just post articles to article directories and nothing happens, Google might sooner or later consider them unnatural links.
Similar with directories - I would make sure you only submit to some decent local directories, or niche directories relevant to your business.
Online marketing is like branding or naming your company out to the public through different online sites, portal and niche sites within. It simply delivers advertisement and promotional message relating to their consumers needs. It also refers to the marketing efforts (SEO) that will drive direct sales and profit via online transaction.
If you are aware on the new Google's Policy you will understand what it takes to get your online presence up. There is not way Google will let business owners to use same methods like 2-4 years ago. The gold periods are gone.
Online marketing and SEO are two different things. Marketing involves promotion or advertising while SEO is a process you do to get the attention of Google in hopes of being put high into Google Search.