OK, a short one here, as I just saw this campaign on Facebook and I remember some people asking for ad examples:

With 5.4 million views seems like a campaign that's been doing well.
It's a short video of the product and leads to this store: https://www.sonastars.com/
Again, a general store ...with some product matching themes.
From what @sapven mentioned and what we see here is that it really seems to be about having a list of known buyers. And then find similar products that would match that audience.
In this shop's case, they seem to have found some success with tools and gothic products.
I am about ready to test this hypothesis with some customer data of my own
Interesting - looks like a lot of the products are of the 'as seen on tv' variety.
@pekadis Would there be merits to splitting a general store like this into "more niche" stores? E.g. a gothic store, a tools store...
I'm completely new to ecommerce, so please bear with the newbie questions! 
Amy
@amy I think this would depend on how you approach this.
If all you do is facebook -> site for traffic, then there's no need to split up.
That would neve be my approach, as I think it's dangerous to rely on just on source of traffic / leads.
I would split things up and, build up a brand / destination site, work on content. That would allow me to get organic visitors via google as well.
But, there first approach seems to be working very well for some companies. Personally, I think that approach is now / very soon or never in the way it's being done now. Big will get bigger and have more data and I don;t think the low cost shipments from China can last forever.
If there's anything else I can help with, let me know!
I think splitting up would gain more trust if customers are checking your store furthermore before buying the product.
Ofcourse deeplinking to the product from FB should work, but I can imagine your not gonna buy goth products from a store which sells mechanic tools and all other products.
A niche webshop presents itself more as an expert, besides easier to sell in future I think than a general store to be honest.
Once again this ad shows video is hotttttttt regarding FB ads!
@pekadis @stickupkid Makes a lot of sense what you both said. Thank you! 
Amy