So been playing for a little bit and I'm lost on how to properly build my team. What I currently have is:

Souls
Standard: Lancelot, Olivier, Vivían, Merlín
Elite: Rosenkreuz

Kamihime
SSR: Acala
SR: Hermod, Amon, Baal, Cybele, Ereshkigal, Nike

Weapons
SSR: Vajra Trident Sword
SR: Labrys, Water Blade Badelaud, Fire Lance Langdebeve, Corrupted Rifle Arquebus, Draupnir

Eidolons
SSR: Vritra
SR: Ignited Dragoon, Diábolos, Bugbear, Sephiroth, Vinglong, Prison of light - Disaster

For soul, I'm currently working towards Mordred cuz I read she a good choice to use. I got a SR Miracle Ticket and I got no clue who to get. I dont know what to look for in a kamihime. I read that Amaterasu and Sol were good choices but neither were there. Doing the Advent event and I got Vritra lb 3, so should I do the 4th or pick up a weapon or two? What skills should I look for in kamihimes? What does ppl mean when they say a grid? I'm a complete noob and any tips/help would be appreciated.thxs