The build is inspired by Luminum CDR Karma build.
Q and W together with proper autoattacking are used for CD reset of Mantra and Moonstone proccing.

The GOLDEN RULE: "EVERY SHIELD HAS TO BE ULTED!"

This build works well with engaging adc's that play aggressive but also ensure protection and decent peel.

Proper Karma positioning is essential for adc's survival. Keep on mind, you have to be far enough to avoid getting damaged, but close enough for poking with Q, providing decent slows and reseting Mantra CD, so you can R+E your allies as possible.

R+Q is the main weapon of early laning, use it for an aggresive poke as much as you can. Your unulted E provides you enough MS to approach the enemy and escape without taking any damage.

When you are engaging (your jungler is approaching), your job is to provide root at first. In such situation always start with unulted W (unless you are low in HP, then R+W), then you Q. Don't waste your Q in the beginning, becouse if you miss it, you lose the advantage of MS reduction, and give the enemy the escape path.

When you are getting ganked always start your combo with R+W on the enemy that is the closest to your turret (probably the jungler). You could technically start with R+E, to provide the shield and MS also to your adc, but in my opinion, if you do the rooting of the invader, your adc is safe and you also get healed twice. As long as you are alive, your adc is. So I do prefer R+W first and unulted shield on your adc at the same time (or both on you, in the case you are being hard focused.)

Your team needs your shielding primarily!

Generally, as you can hit the normal Q, fire it! Your main aim is to keep reducing the Matra cooldown, so you can provide as much AOE shielding to your team as you possibly can and also to proc the moonstone passive. Never use R+Q late game, the only exception is, when you are 100% sure you hit at least 3 enemies (the matra cooldown is refreshed again). Your main aim is to provide R+E to as many allies possible. Be focused with the decidion who do you shield, even though the shield spreads to the others, only one ally gets the full shield amount.

As in early and mid game you stick with your adc (except of occasional roams), in late game this CDR build and especially moonstone works pretty well with allies that have a great sustain. Have an eye on your frontline, mainly tanks and fighters and keep them alive with your AOE shielding and proper moonstone passive proccing.