You can't do much about your weapon grid, but you can level the water kamihime. Going forward, you should focus your weapon resources on maximizing your wind weapon grid. That means collecting wind assault SRs, leveling them to 40, LB'ing them, leveling them to 55, and so on until you've maxed everything. Your eidolons are severely lacking right now. You need a full set of 6 SSR eidolons immediately if you want to progress, and Yatagarasu will be critical for you due to the attack down active skill (possibly the best eidolon skill in the game). Collect copies of Yatagarasu and level them to 40, then choose one copy to LB. Aim to collect 5 copies from the upcoming event. Once your team is filled, start using the spare copies to continue LB'ing the original. Your goal is to reach the point that you can run Ultimate difficulty in Advent events ASAP.
To repeat, this next event will be critical for your progress. Invest the time to collect 5 copies of Yatagarasu. The other rewards are less important (make sure you're collecting your daily half-elixirs though). Outside of Advent events, make sure you're running the Wind Disaster standard battle 3x each day. That's how you grow your weapon grid.