As you are aware, you are able to reach a large number of people on social media (especially Instagram) but there is honestly a short list of a few that really matters. We like to call Twitter, Facebook and Instagram "The Big 3" since they are the most commonly used social media outlets. Pinterest is also a great way to reach potential customers with most e-commerce platforms offering add-ons that can auto-post new products for you.
We recommend you begin with The Big 3 followed by Pinterest.