"Gravel and mother plant soil" might have a remote chance of working for a few seeds, maybe. But I think you are missing the point completely.
Your Phalaenopsis seeds have no such possibility, especially in soil.
You must study and try to duplicate the conditions that they might find in tropical Southeast Asia, not those in the SE Europe.
If you were trying to sow seed from your native terrestrials, that would be better.
Scientists have established a unique relationship exists between an orchid seed and a mychorilhzal fungus. The fungus needs to be present in order to successfully germinate the seed. How do you plan to introduce or collect that fungus to germinate your Phalaenopsis seed? If you were in SE Asia and could spread the seed on the wind and some how narrow that dispersal to a very small area, maybe just maybe a few might germinate. But I doubt it. Yes it happened in their native habitats but not in large numbers.
I can understand your desire to achieve a new hybrid, but Phalaenopsis breeding is now in its seventh, eighth or twelfth generation, hundreds of hybrids have been produced. Quite literally every conceivable color has been produced but if you need to try, then try. But you have to be realistic, your odds of success are so remote. It is never going to happen in my opinion.
