Focus on quality content creation first. As they are the most important things that would stand the test of time. Then you can start working on the basics of your onpage SEO by installing Google's XML plugin, changing the meta description of the blog by using a meta description plugin, and make sure your site is mobile-friendly and light enough for your visitors to load.
Then you can start adding social media sharing buttons to your site. You can install one of the many social media addons for WordPress, I suggest you try Jetpack's social media feature. They are easily configurable and came as a default plugin on most hosting's setup.
Finally, make social media pages / accounts for your blog for people to follow. And work on your offsite SEO by doing blog commenting on blogs that are relevant to your niche, and forum posts on forums that are also relevant to your niche