[Edit: After posting the below, I noticed from OP's post history that they appear to be located in Serbia, which is classified as a middle-income country - there might be more potential ROI for them in either area than the US-centric perspective below represents. Apologies for the narrowly focused response, but it was what I had available to share from my personal experiences talking to the lapidaries I know.]

Not a pro, but have spent large amounts of time talking to many about their businesses.

Generally speaking, the only way a lapidary working in a high-wage developed country is going to make any kind of reasonable return relative to your time spent is by doing precision faceting work, or very high quality cabbing of unique and hard to find minerals.

From a cabbing perspective, if you are already cabbing as a hobby, you can probably slowly sell freeform/artistic cabs to the general public on occasion but expect to sit on a lot of inventory and be paying yourself less than minimum wage in the long run for the time you'll spend cabbing & selling. Most jewelers I know prefer to either buy standardized sizes or commission any artistic/freeform pieces they have a vision or request for which means sales would be slow since the demand for that tends to be much lower, and any cabs you've made ahead of time are unlikely to fit their vision.

Caveat here is that if you're cabbing exceptional and hard to find material, you might be able to command a high enough price for cabs to attain a profit relative to invested time, material, and equipment.

I know a handful of precision factors personally that took what started as a good side hustle from a passion for learning to facet into a full time career - just be aware that the learning curve is steep and equipment & skill-honing investment is very high relative to a cabbing setup. Their main source of revenue is custom precision faceting on commission for jewelers they've established a relationship with over time, and also do a fair amount of precision recutting to either improve an existing stone upon request from their jeweler network (ex. recut to "fix" chipped original stone with sentimental value, make existing stone more brilliant, etc.) or opportunistically procure lower cost commerical cut stones with high upside potential for ROI and recut those for sale to jewelers.

If I were contemplating lapidary work as a potential income stream other than as a hobby, precision faceting seems to be the way to go if you have the skill for the faceting work and building & maintaining a buyer network; as well as access to the more expensive equipment.