Gypsy people do believe in possession, and they do believe that those possessed are under the influence of the Devil. But again, it’s not about evil.
They do believe in werewolves and such, but it’s more just an accident than a moral failing. They believe werewolves are bad. They do believe in vampires, but vampires are draining spirits not movie villains, and they have ways for dealing with any source of negative influence.
Crystals and such? Potentially. They did adopt magick from other cultures and adjusted it to keep with their understanding of the worlds balance. What exactly you would learn would be dependant on who taught you. Much like the Gurus of India, and true to their Indian origins, they do respect/revere fire. This is why you hear so much about campfires. The living were not the only ones considered to gather around fires. Their departed did too, and unclean spirits are seen as afraid of the communal fire as it has the spirit of the Roma people behind it.
Music is very important in their culture, again not for a strictly formal reason, but because of how it affects peoples spirit, and they do believe that a poorly performed or timed song can cause bad luck. They also believe in the power of their crafts. When one of their clan dies, they do not give that persons possessions to another member of their clan. They destroy them or sell them to outsiders. Otherwise, they see it as stealing from the dead and bad luck. You should not covet the possessions of the dead in the Gypsy way.
What about their love of music and dancing? Just for fun or is that also to show respect to God? It’s partially religious, yes, and they will sing hymns. But song and dance are considered lucky as they uplift and strengthen the spirit. To refuse to lift up your spirit in song and dance, they consider unlucky. They strongly discourage the person, who rejects their activities, from doing so. They don’t have to do any specific thing. If you are lame and can’t dance, that doesn’t worry them. But you should be willing to sing or drum or play an instrument. They are a tight knit people among their own tribe, and they sing and dance like orthodox Christians pray before dinner. It’s just considered spiritually proper. The timing of course doesn’t matter in any absolute sense.
Your thoughts are welcome. Be well friends.