sprinkle, thing, shallow, frivolous
澆 centers on liquid applied lightly or in a scattered way: sprinkling water. The extended senses of shallow and frivolous come from the idea of something thin or insubstantial, like a light sprinkle rather than a deep pour.
澆 combines 氵 (water) with 堯, which likely contributes the sound. The character originally referred to sprinkling or pouring water lightly.
Water 氵 beside 堯: imagine a gardener lightly sprinkling water from a can over a high mound (堯 suggests something tall or elevated), making the ground just shallowly wet.
For ギョウ, picture a gardener sprinkling water while humming a made-up tune: 'gyo~ gyo~' as the water falls. The sound 'gyo' cues ギョウ.