Serial Entrepreneur, I had my first .com in 1995 and it was a directory of locations and suppliers to the film industry. Since have launched many £multi-million businesses including an Online sales and marketing outsourcing company that takes care of everything for our clients online sales and marketing.
I think you already know the answer to this as you spent the most time on the third option and you are correct. The Internet is awash with too much information for buyers, they have information overload. So you should concentrate on niche websites for 2 reasons. The first being ease of use for the customer, finding what they want to buy in seconds not hours, the second is SEO, your sites can interlink and if built right pass on link juice and customers by promoting your other sites on each other. You will rank much easier with a keyword domain combined with keyword content. I am doing exactly this at the moment within a number of niches globally and have a team of expert developers, content writers and SEO experts working under my direction and it is working really well. You will need to build a mini-net around your money sites and build links to them, just make sure there is no pattern, then build links from your money sites to each other from keywords not banners and you should rank really high on Google.
There are Facebook advertising techniques that would allow you to target competitors followers, related beauty or skincare pages followers then target them with your advert going to a landing page with a buy now unmissable offer to capitalise on your conversions. Because most people do not buy first time, I would then re-target them with the offer on their Facebook newsfeed so they do not forget you, adding to your conversion. Facebook is by far the cheapest for adverts Google would be crazy prices for this type of product. You could also look at placing with affiliates and let them do all of the marketing work and your cost would be fixed, but there is a lot of competition for affiliates in this sector so maybe difficult. If done right on Facebook with a laser targeted campaign with landing page you should be looking at $0.25 to $0.30 per 1,000 views with a decent conversion making the cost per conversion very low. When you target people you know would be interested in your product it is always best to do a CPM campaign rather than a CPC as this is a waste of money, if launching this product there is no market price other than competitors products so you can show it as a high price then do a landing page with a launch offer only available for a limited time with a count down clock, even offer referral discounts if they share on Facebook.
Hope this helps