For over twenty years, I have been connecting companies with customers. The tactics may have changed, but the fundamentals of business haven't. I'll help you identify your unique position in the market and guide you on connecting with customers.
Congratulations on getting your start-up to the next level. I can relate to how difficult it is to get to that position.
As others have stated, Facebook* should be treated differently than Google. Google helps connect you to people actively looking for your product or service, while Facebook enables you to expose your product or service to people unaware of it.
Although a Google presence (organic or paid) is essential, starting with Facebook can provide useful data (keywords) that can be applied towards your Google presence later. Facebook will also help determine the interest in your product in the market. Facebook is relatively inexpensive to begin with and easier to use than Google.
I also recommend starting small with your advertising on Facebook. Experiment often and always be testing to improve. Once you find a formula that works for your business, you can begin investing more money into a proven campaign. You can run effective test campaigns as low as $50 for a few days.
I hope that helped and congratulations again on growing your start-up. If you would like more guidance or tips that apply to your unique situation, I would be happy to help. In the meantime, enjoy your growth and stay healthy!
*Although Facebook is the largest social channel, it's not for everyone. Your audience should ultimately dictate which channel to use.
I would recommend a Shopify site. I've created a few already and found the platform to be very user friendly and focussed on e-commerce. Considering you're selling something lightweight, shipping would not be a major issue and rates are easy to calculate in Shopify.
The big thing to consider for your business is whether or not you want to build a customer base or sell products. Selling on marketplaces can be easier to set up but you are building someone else's customer base and in a sense building a house on rented property. Creating your own store gives you control and you build your own customer base that you can contact at any time.
Shopify is very flexible and is fairly easy to set up with lots of tools and support available.
If interested, I can go into greater detail about setting up and managing a store on Shopify. In the meantime, good luck with your business!