To unlock Kaguya, you must be level 150 or VIP 9.
Use Kaguya orbs and silver to evolve Kaguya. Use stats orbs - Kaguya to get extra stats (PV, ATQ, DEF). These stats orbs are available in the Path of Naruto or events.
Activate skins to gain additional cumulative stats. Skins can be activated several times to improve the basic stats.