Even for an Online Store,
Content is King! Period. Again.
1. Make it clear what your site is about from landing on it and from the meta description you use to bring a customer to it. What will they find there? Why should they buy your product?
No content. No Meta. Nothing to find. Bad impression. Lost reputation etc etc. Hence, content is King. Customer is right!
2. Make it easy for the customer to find what drew them there - break your site up into logical (to the customer, not just to you!) categories, and with opencart, I would add multi-stores, when it makes sense. Don't overwhelm customers with everything under the sun and thousands of categories.
No content. Nothing to search. No logical separations. Content first then Usability.
3. Things like payment methods, how to contact you, and other vital info should be clearly upfront
No content. Nothing to choose from. No payment method. No content. Why contact?. Content first features Second.
4. Provide details on products (this is where content & originality come in). Know your products and if the manufacturer/supplier doesn't give you a lot of info, research and add your own. If 1000 stores online sell the same products but your site has original, expanded information, yours will rank higher with both search engines & customers. Don't go so far as you have a 1000px long page, but think about what you would need to know if you knew absolutely nothing about your products.
Details IS content and so is Descriptions and so is a lot of info and so is a lot of products and so is a lot of product images and so is originality and so is information and so is so on and so forth, all content.
I think we often get too bogged down in what looks pretty to us and works for us...but forget how the customer will view it.
True. So true.
Content is what ENGAGES. What sells. What makes up your site unique, interesting blah blah blah. So, in my honest opinion, Content rules, Content is indeed King!
Next comes, usability, responsiveness, aesthetics, features etc etc
REMEMBER: Content is NOT Lorem Ipsum and placeholders. Even ready made templates are at times extremely difficult to fill in if you do not have proper adequate content, and with partial or incomplete content the template which seemed as 'the one' would look exceptionally bad.
Consider firing up a mind mapping program and laying out your site ideas onto it. Soon you will find that you lack the necessary content for your ideas. So in reality you actually develop content before you delve on it's presentation, usability, aesthetics and all that.
In my www development and design experience, I now base all my ideas about site development on the content provided by the clients. Hence, I again maintain that Content is King!
Just my 2 cents