Blog for the fun of it and show character. It is immaterial how many write about a particular subject, it is how you write the matters.
Search engines don't spare any blogger. E-commerce bloggers must keep in mind the search engines in mind while writing blog posts. SEO friendly writing improves the search of your blog content.
Formatting - Your post need not be a circus. If you are not good with formatting, then stick to a theme that is light and descent in colors and the post layout. If you are good with trying new stuff then use that skill to better express through colors, fonts and layouts. Avoid colors that are dark and fonts that are overtly bright.