Can someone please explain expeditions for me?

I give a bunch of materials then I have all my progress reset and to my understanding I get an increase on the cap of my level but that’s only based on my stash value. Is the increase cap the only thing you are getting or am I missing something? Seems like you are giving up a lot for 5-10 level points. I’m not saying it’s good or bad, I just want to understand how it works.