If you aren't yet published with an established fan base: post everything you feel comfortable with publishing
Your goal should be to build up a fan base so that people know your name and know what you are working on. That way you can build up a reputation while working on the finished product and at the same time get a lot of feedback. How useful that feedback is will depend on your audience, but at least you've got feedback you could try to work with if you wanted to.
Working until you have more-or-less completed works might mean that you will not have so much to post and people nowadays expect a constant stream of input if you want to keep your product in mind. Only when they already know you and think about something when reading your name or the name of the universe they will be a bit more patient.
If you already have a fan base: post little excerpts
If you already have a fan base that is eagerly awaiting your next product you should try to give them things that are close-to-finished. You will still be able to incorporate the feedback into the final product, but you want to tease your fan base with these excerpts to start up the hype-train.
In any case: try to leave the most important plot points out
You don't want to completely spoiler your whole product with the marketing, so try to keep some things secret. Or maybe write little short stories that show your style, but from different characters that explore little parts of the world or build up some things in a "Ten years before the events"-style without revealing too much about the real plot.
That also means that you should include basically everything you can create that is somehow related and can give you fans that would consume the real product that you are working on. The more you can guarantee a steady supply of something the better. And as long as you focus on a single topic, which is the world you are building, posting a lot of different stuff might attract lots of different people. Normally you should be careful about changing the type of content too often as people often will only look for a specific type of thing when looking at blogs - but as you are focusing everything on a single topic switching the type of content is a good thing to do.
You can also use the above advice as a sort of ordering - first you start with a bit of this and a bit of that and a side story here, until you have some regular readers/ viewers/ ... and are ready to post nearly-ready little excerpts as teasers.