What I’m sure would be most effective is to figure out a niche. Develop a product that is desirable and focus on that... except, what?!
I'd recommend that you start searching for "Open Source" products that have forums, one example is FarmBot:
https://forum.farmbot.org/If you watch their videos, you can see a lot of the components are made from plastic via 3D printing.
I've considered the idea of making and supplying these components in metal, but that would be down the road as I'm not currently set up to do it.
On the PRO side:
1. the 3D CAD drawings already exist and available on their website for free download.
2. reading your other project threads, I believe you have the mind and ability to possibly improve the currently available tools/attachments and/or design your own.
3. the market already exists.
On the CON side:
1. not having one yourself makes it nearly impossible to test the products unless you can find someone in your area that has one.
2. you might have to deal with international shipping.
3. you're on the hook for the cost of the prototype with no guarantee of any sales.
FarmBot is just one example. You can search for others in fields like Prepper forums, homestead forums, model building forums, or any other niche market.
It takes time and effort, but I've seen questions for products in these type forums with responses stating that basically they don't exist. This tells me there's a market for some of this stuff if someone can make and market it at a reasonable price.
I know you've eluded to learning and getting into CNC. IMO, keep going with this as it will save you a lot of time and material if/when you need to mass produce pieces/products. Along those lines, you might consider getting a 3D printer. This would greatly help in your CAD learning process, allow you to "Print" design prototypes at a reduced cost, and allow you to make your own "Plastic" parts, if needed.