Time will tell... you have a core on water, a core on fire, and 2 semi-cores (I guess?) on light. It's anyone's guess what you'll main until you pull more cores, but irregardless of what event it is now, you should almost always strive to get the weapon and eidolon on MLB.
It might be easier to advise if we have your SR and eido list as well, but water seems to be a pretty solid path for you.