I think you're on the right track with the likes of eBay, Instagram, and Etsy. Those sites have established communities interested in what you have to offer.

That said, each of those platforms have different optimization techniques to reach the right audience. For example, using proper hashtags on Instagram will likely result in increased traffic. Spending some money on Etsy's pay-per-click ads will result in fresh, targeted traffic.

I've helped brands around the world increase their reach through optimization with varying budgets. I don't believe in "one-size-fits-all" approaches, as each market has a unique audience, product, and seller (you) - those are important considerations before launching any type of sales campaign. I'd be happy to schedule a call with you to discuss more in detail.

-Shaun