Of course you may continue with the submission and SEO stuff, it should not be concerned with the number of posts because older these techniques, more number of visitors you will get.

If your website is complete according to designing and other way. Then you can start optimization of any web site. But must try first on page and then turn to off page.

You can post new post on your blog and submit its link in directory websites. The age of blog doesn't matter in link submission or Page rank. It will matter when you start a new website or blog and your website or blog has a huge number of backlinks within one month or fast, then it will come in Black Hat.