sacrifice
犧 centers on offering something valuable, especially an animal, to a deity or higher power: a sacrifice.
犧 combines 牜 (cow) with 羲, which likely contributes the sound and relates to a ceremonial or sacrificial context. The exact historical development of 羲 is uncertain, but the character as a whole points to an animal used in ritual offering.
A cow (牜) is offered in a solemn ceremony (羲 suggests a ritual atmosphere). Picture a decorated ox being led to an altar as a sacrifice.
For ギ, imagine a sacrificial ceremony where the priest wears a long, flowing robe that looks like a giant 'G' (ギ). The 'G' shape cues the reading while the cow is being offered.