One of the main reasons that most web design companies are bad at marketing e-commerce websites, is that they don't understand the fundamental difference with the way you usually market an e-commerce site, compared to a normal brochure-style site.
There are lots of marketing channels that you can use to advertise a brochure-style website, but these are just nowhere near as cost-effective as the e-commerce-specific channels. This can make advertising an online shop, very expensive, and in a lot of cases, just not sustainable.
The key difference with most e-commerce advertising channels is that you are not advertising the website, you are advertising the products.
If you are using SEO as a key marketing method, you will normally have a small set of keywords that you are optimising for (unless you have a HUGE budget). So, it's difficult to optimise for all of your product pages. Whilst you can do some basic SEO that applies to all of your products, and tweak the product descriptions, you would need a huge SEO budget to build inbound links to each of your products.
If you are using Google AdWords (or Bing Ads), you can target many more keywords. But, if you want to create an Ad Group for every single product that you sell, that's going to get very expensive, and very difficult to manage. But paying for clicks on website-specific keywords or product category -specific keywords is usually much more expensive, because these terms are much more competitive.
If you are using social media, again, this tends to be directed at driving traffic to your website in general. Admittedly, you can post links to specific products, but if you've got 2,000 products on your site, nobody is going to follow you if you post 2,000 product links every day.
With an e-commerce website, advertising your products is generally cheaper. It also tends to attract more buyers than general browsers and researchers, which in itself makes it more cost effective. You should be focusing on product-centric advertising for your online shop first, and if you have any budget remaining, then consider advertising via the more "traditional" channels.
OpenGlobal E-commerce have years of experiencing with e-commerce marketing so we can bring out the best results for our clients. If you need help with your online marketing, call us today on 0845 269 9624.