Spells: Flash + Exhaust/Ignite. I think Exhaust is the play.
First off, runes like this:
Glacial Augment, Magical Footwear are a must. If you struggle with HP/mana management in lane, Biscuit Delivery could be nice, but since you also have Manaflow Band, I recommend Perfect Timing (lets you turn dives around).
Last, you can take Cosmic Insight
If there's a champ in lane who can just blow you up in one rotation and kill you, go Unflinching.

Items should go something like this.
If the enemy AP is a problem, slot in Locket somewhere in the middle.

Ruby Sightstone reduces item active cooldowns by 20%, so it's a sweet pick for Glacial Augment Lux support who runs lots of actives.

At home my internet lagged sometimes, so I only tried it on my Gold 5 smurf for a couple games, but it's workable. Honestly feels way more impactful than running Arcane Comet, poking from range and stacking damage items.
Plus, shooting out ice lasers is seriously the most fun thing ever.
란두인 쿨타임 줄일바에 구원간다
More
허미..
More
얼음광선 갱호응도 좋은데 도벽콩콩이 때문에 아무도 빙결안써줌 ㅠㅠ
More
오 해바야지 내일!!
More
빙결강화 베인도 좋아요 장난이 아니라 ㄹㅇ루
More
도벽도 좋음 평타사거리길어져서
More
빙결..
More