I need experienced DMs!

I want to create a pirate campaign for my next project. I want to make it an evil world that is different from the rest. The world is a world of islands similar to One Piece. In this world, good intentions are not common. This is a world of Vashar, Jerren, dark elves, Illithid, etc. In this world, the dark elves won the war against the elves, and the Vashar realized the gods tried to genocide them as they were a failed prototype of humans, Jerren are a real thing in this world, etc. All normal races, or attitudes in this world are minorities or at risk of losing their lives. I just need help brainstorming with world creation and am open-minded to all ideas. This is my first campaign as DM and I want to create an evil world that is long-lasting. I want to create a world with a very dark and evil feel. I can create individual islands and archs but the main quest is where I am struggling. HIT ME WITH ANYTHING AND EVERYTHING. I NEED THE FEEDBACK.