Set Charm stats?

So I’m just curious whether anyone has figured out whether there are restrictions on what stats certain charms can have in a set. I’m trying to get all +3 either occult or abyss skills on all 5 of my set and after 1200+ Raw primordial dust I’ve only got 2 to reroll with the skill levels and now stuck farming more. My “Fer” and “Beru” both got skill levels but easily 600 raw went into the “Linta” without success.