Jodi I want to point out something that you've done with your kewyords which not many people do. Since you're in New Zealand, you placed "nz" at the end of your keywords and now you're ranking on the top page of Google for all these organic keywords:
rifle scopes new zealand
spotting scope nz
nikon scopes nz
rifle scopes nz
nikon scopes nz
vixen rifle scopes
nikon binoculars nz
I'd like to bring up that Google recently made an update to their algorithm which is making it more friendly to local business. Thus, if you own a physical storefront, putting your location at the end of your anchor texts will improve improve your visibility as far as local SEO goes. If you own a infant clothes shop in Austin, TX, making some keywords be "infant clothes in Austin" would be a fantastic way to rank at the top of the SERPs (Search Engine Result Page)
I used to run an SEO company and I would like to think I know what I am talking about ;). SEO in my opinion is presenting content to the end user that is relevant to the keyword you are trying to target. Always design the site for the end user in mind!
Rather than me rehash known info, I have included a PDF of Google Guidelines that is very relevant and a very good read. http://docdro.id/eBTLUrR
Essentially you need to know three things. Firstly search engines want to match sites with really good information, upto date information and great user experience to search queries, the better you make your site in terms of unique copy and images with desctriptions, background information, blog posts, user reviews, links to relevant content etc the more useful if will be to your customers and the better search engines will like it. Secondly search engines can only index information that is on your pages, so if you don't use words in your copy and the descriptions and titles of your pages/images, if you don't list your address on the site, and you don't spell out exactly what it is you do then your never going to display in search results for those things. Finally when a search engine finds duplicate content it will divide any available content between the sites or pages that use that content, so if you copy and paste content from another site even if you rearrange the sentances a little you will get a lower score than a site that wrote unique content even if their content is not quite as nice. This also applies to your pages if you have 2 pages that say almost exactly the same you will have cut the score for each page in half. Remembering that any page gets an element of its score from the site as a whole and an element for the page itself.
In summary concentrate on making good unique content more than on your search rankings and update your pages regularly to ensure you stay current.
There have been some great answers in here so far! :)
Here's something I've found very helpful recently, a new blog post from Ahrefs (an SEO tool) that has 200 easily actionable tips to improve search engine rankings. A lot of them are relevant to E-commerce and are easy to navigate through with quick links to each section of tips like:
They do push their tool quite a bit throughout the post, but most of the tips don't require the use of any paid tools.
Hope it helps!