I'd ask Rocco Baldassarre. He is the best online marketing consultant I've ever seen and can surely give you concrete advice.
Said that, my advice would be
a) your own e-commerce store so you can drive traffic to it without losing money on commissions
b) learn from best selling products (you can see sales ranks of competing products if you register as an amazon affiliate marketer; it's free) and copy their structure, split test regularly
Hope it helps!
On Amazon, I have no idea. But elsewhere the right strategy seems pretty straightforward. Search, search, and more search.Since that niche is highly specific and utilitarian (rather than brand- or image-driven), I'd recommend concentrating on (1) search, (2) search, and (3) search. Other marketing channels such as social media, radio, etc. won't give you anywhere near the bang for your buck.
These days, that means mostly SEM. Leveraging the right domain(s) can shave off some long-term expenses. SEO will be important too. Make sure you appear preferentially in the most relevant search verticals in the most authoritative fashion.
Basically, get the maximum of clicks with a minimum of cost; then be sure those clicks convert to sales through your site. Concentrate on gathering and evaluating data from SEM campaigns and on-site sales funnels. Try some A/B testing on your website and domains / URLs being displayed. Gradually your ad spend will become more efficient.
I've been selling on marketplaces such as Amazon/eBay since 2000. Each marketplace must have a different strategy. Marketplaces can also be looked at customer acquisition channels for your brand. Having a website is crucial and must be part of your long term strategy.
I always say this.....Marketplaces sales are like one night stands and sales on your website are more like long term relationships. The lifetime value of a customer should be the ultimate goal.