Here is my Mei's team. Finally put my thought in it.

Itachi x Mei Water f2p buff Team.

Mei - x - Fuguki

Water - Itachi Anbu - x

Skill 32212

Summon Gamaken

Chase: R-RL-LH-HR-RK-KL-LH-HR-RK

Even if Fuguki only hits 2 units that's still 16 hits, easily trigger Itachi 30 hits.

Initiate with Itachi, your team will instantly immobile by Mei, cos Itachi removes buffs on that unit.

Mei buffs all units, plus Azure buffs 3 units. Fuguki will hit hard extra 80%.

I am water main 1 trick. I only know what best for her. lol