Awesome - looks like you have the ball rolling very nicely & most definitely on the right track

For your own online shop I light suggest shopify as a good solution that takes care of the technology part while you can focus on what you do best.

I would also broaden your potential client base as there will be a lot of people who like things a little different but who don't necessarily love horses

https://www.facebook.com/ads/audience_insights

This is a great tool to help drill down a little further to help your ad targeting and really define your perfect customer.
Use the "interests" on left hand side with one interest. and then look at the "likes" tab across the top.
This will give you a list of related pages that you can use to help target.

Final point - aim higher..

You have a really interesting product
One of the awesome things about Facebook ads is you can pop your advert right in front of people who like these things who are known "buyers" of cool things.

You could aim to hit your sales targets in 30 days with the right promotional strategy....

Good luck
Phil