I heard (I think?) that there's Japanese source material that goes into more detail on the setting. This likely won't be made available in English.
The story progression from here will be in Raid events. I think that's it. The purpose of the collaboration events is to advertise other DMM games, which typically aren't available on Nutaku.
I'm sure you've realized by now that these games are shovelware. New gameplay mechanics and content will continue to be introduced at a steady pace for those who like a challenge. Other than that? It's a F2P Gatcha porn game, and this is about as good as they get. They're very effective at parting people with their money and cheap to produce, which is why DMM continues to churn them out and why Nutaku continues to host them in English.
Did you notice how badly translated the Guild Order introduction was? That could be a taste of what upcoming story content will look like: barely understandable.