Creating blog content is a very useful and effective way of consistently building content on a site. When creating blog posts, it's a good idea to do some keyword research to figure out what it is that your audience is interested in and searching for online. Also, be sure to research competitors, forums and social media to narrow down on topics for your blog.
The topic you choose must have enough depth that you can create a lot of content for it. This is important for building an authoritative site, for search engine optimization, and most importantly, for the end user. If you don't have enough content about a topic, you're not going to be taken very seriously as an authority on the topic and it's unlikely you can convince someone to make a purchase from you.