Long tail keyword landing pages
Hello everyone. I am the owner of a website which sells resistance bands, and I've been working really hard for the past year on building up the organic traffic of the site, mainly by creating blog posts. I don't run any ads (yet) because I'm intrigued by the challenge of creating a successful website purely through the art of SEO. I read Brian Dean's ultimate guide to SEO about a year ago and it was a Eureka moment for me.
Anyway, I've been moderately successful in increasing the traffic - currently around 30k/month. But unfortunately that translates to only about 3 or 4 sales a week. Up to now, I've focussed on informational keywords - if you search on Google for resistance bands for back or chest or any other part of your body, you are likely to bump into one of my articles.
Now I would like to progress into my 2nd phase, which is to focus on much more buyer-oriented long-tail keywords. For example, instead of "resistance band back exercises" I would like to create landing pages based around keywords such as "buy resistance bands online" or "cheap resistance bands online". My plan is to create at least 50 landing pages, each one tailored to a specific long tail keyword - reflected in the URL, image tags, keywords repetition etc.
I have two questions which crave your kind attendance:
Firstly, if a page is not navigable from the website, i.e. in Wordpress it will be left as an "uncategorized" page, is it still crawlable by Google? Are there certain measures that will make it more crawlable? I am assuming that having a few internal and external links is a sine qua non.
Secondly, these pages will all be basically the same - just a showcase of my products with some information about resistance band training, no more than 400-500 words. I know that having duplicate content is a big no no, so I plan to slightly alter the content for each - move around the paragraphs, change the wording, change the image alt tags and so on. Is this enough? Or must one radically alter the content with completely fresh information in each in order to convince Google that it is a unique post?