Search Engine Optimisation SEO Requiredfor e-Commerce website

I need to add Search Engine Optimisation, Metatags, etc to my e-Commerce website before it's launched. There are over 40 products on the website. In addition have "buy gift voucher", "sales voucher", "launch promotion", "sales voucher", "loyalty rewards", "trade account", "non-trade account". Products are specialist frozen food free-from foods for parcel delivery to Mainland UK consumers. Website has external links to our social media pages, and external websites. This is for fast efficient results, quick climb to first page of search engines, and a successful first week launch for max exposure, sales conversion, and all on minuscule budget. I'm afraid my business does not have the backing of a big investor or deep pockets. If a respectable exposure and sales conversion are achieved with the launch then this could become a regular work for the right freelancer. Have over products on the website, and several domains pointing. The website is build on an E-Commerce platform service. All i had to do was add our products, policies, services and images. Regarding SEO and Metatag etc, we're not confident or experienced with this.
The website domain name and admin access will be provided to the selected service provider. Only professionals with excellent understanding of SEO, online marketing and demonstrable sales conversion success record please apply.