Hey, I'm coming in a bit late into the thread, but I'd like to give my 2 cents on the moss part.
While they are usually beautiful, abundant, and FREE, the moss that grows around our houses generally don't fare well when we try to grow them inside. Whatever the
specific reason actually is, it is probably because those mosses need different lighting/humidity/airflow/watering than we typically provide in terrariums. They will typically stay alive for a few months, and then unexpectedly brown and die out.
I don't know what mosses there are in Mallorca, but I just wanted to prep you, in case they behave "normally"
A different option would be to go to a local greenhouse that has orchids, and ask if you can collect some of the moss growing in the containers for your terrarium. I feel like most places would be OK with this, especially if you are buying some orchids from there anyway.