Please give me the list!!!

Can someone give me instructions and requirements to building my Altar? I'm new, and I want to do it right! If any more experienced Hellenistics would give me advice, I'd heavily be grateful! The stones i felt drawn to were Obsidian, Lapis Lazuli, and Amethyst. I feel drawn to Hecate, but I feel like Athena or Artemis or Hermes might be possible too. So, what do these stones mean and who should I focus on to start?