1. Build up the community of 100 initial evanglist - build the initial relationship with your identified revelant to your industry: 100 bloggers list, Journalists, brands that compliment what you are selling
2. Start with an initial paid media channel - ie Facebook - learn how to setup and run your own ads, don’t have to get complicated, start small with maybe a $5-10 budget a day and scale as you learn along the way
3. Expand on the alternative paid media channels and start small as you did in step 2 and scale gradually.
4. Build upon partnerships you have established in point 1 and explore areas you can work with them (ie co marketing, email marketing etc)
5. Test the above 4 points and share your learning back here with us.

1. Build and launch your own ecommerce site or setup a seller account on any marketplace (ie Amazon)
2. Start selling to learn what works and what doesn’t
3. Repeat with step1 on a second product etc
4. Start a blog/podcast/community and share your experience you have went through in points 1 to 3.

You can purchase the barcodes from the sites here:
barcodes4u.com
buyabarcode.co.uk
speedybarcodes.com
snapupc.com

And this guide might come in handy:
https://www.gs1us.org/upcs-barcodes-prefixes/get-started-guide

Would tak precaution if you are even considering to purchased upc barcodes from ebay as there might be recycled barcodes being sold and might lead to your products being identified as fraudulent and shutting down your amazon seller account.