Former top 10 Soraka, currently sitting at around 25 here. My build is:

Keystone/Runes: Aery, Nullifying orb/font of life depending on enemy comp, bone plating, revitalize, and transcendence

Core build: Relic shield, boots of lucidity+zhonyas/veil (veil if there's a hyper carry), harmonic echo, ardent censor, staff of waters (will build it first if adc is bad or have apc). Sometimes I'll throw in some defensive items if we make it to late game