Use common tropes and stereotypes and use the "keep it simple, stupid" method of writing a non-fan based universe.

Complexity will arise through interaction and exploration of the world. The more complex the world, the higher the bar is set for people to surpass in order to achieve entry into that world, and the more time they will need to invest to truly understand it. Ergo, the simpler the world, the larger the potential audience, the more ideas and view sets you will obtain, the greater the variance in characters they create, the greater complexity becomes when disparate characters encounter the same situations together.

ex: If you are making a fantasy universe, make sure you have an easy method of entry, use plot elements or races everyone is familiar with, that they can use to then explore the more unique elements of your universe. Don't be afraid to then take the more unique elements and have them get discovered over the course of the story.

Anything else I can answer? :3