Without a shadow of doubt, the most important hire for any new eCommerce website is a strong copywriter.
Your ability to succeed online will be directly linked to how well your website is judged by Google, and other search engines, and whether you appear high in the search rankings when potential customers search for your products or services. With Google clamping down almost daily on any attempt to 'game' their index, only quality content can be guaranteed to provide good and long term positioning for your site.
In addition to this, quality content is essential to converting visitors to your site to paying customers.
Most organisations lack the skillset in-house to produce good quality content, so adding these skills to your eCommerce business is a must.