Which of my book worlds do you think I should focus on the most for the first story from it?

Fantasy world built around winged races.

Fantasy world connected to my second book world though it mostly a human realm. My second book world is the one built around winged races

World where a black metal band is the 5th largest economy in the world. Alternative people are very popular. Metal, goth, punk, alternative are all very popular but there are also many celebrities based on real world people and families