My first guide, so judge harshly. That being said:
This guide is about Lux as a support and only as a support; therefore, I will not be covering all aspects of using her in every situation.
When I use Lux as a support, I use her with the philosophy that "The best defense is a good offense" Lux can better support her ADC through AP damage than just mana regen and throwing out a shield constantly.
"PFFFT.... Lux as a support. There are better (healing) supports out there."
To this I answer: Yes for the 1st 5 levels your Healing Support & ADC will give us a rough time indeed, but when Lux and for instance lets say Ez both combo ult simultaneously with follow up attacks, it won't matter how much heal is bestowed upon your ADC or support, they're going to die.
The only problem with the dueling burst ults and damage output is to make sure your ADC is the one to take the kill. If not HEY! your team got the kill anyways. WOOO!!!!
Even though this page is for a support Lux, all you have to do is switch Exhaust to Ignite and you can go Mid.
Runes are set up for maximum sustainable AP damage in a lane AKA Suppressive AP.
Again this page is setup for Suppressive AP.
Just a standard AP mage build. The 3 doran's rings into a rod of ages will provide plenty of health and AP for moderate AP damage and health that will scale as the game goes on. Some people like to throw Sheen in place of the other 2 doran's rings. That is a matter of personal preference between snapping Lux's passive off harder and health/spell damage.
No matter what the situation we get into I always pick up rabadon's because you need it to farm and sustain enough damage on the enemy team. If you keep dieing with lux and need a different item at this point, chances are you're not playing Lux correctly. If you feel the need to get Abyssal or Zonya's first you probably could, but it will stunt your champion's overall growth.
After Rabadon's it's highly situational:
Do you feel confident enough that you will never be caught by the enemy team? If so, go with the void staff and/or Lich Bane.
Go with the Abyssal Scepter and/or Zonya's Hourglass depending which character is fed more on the enemy team.
The reason why I go with Light Binding first is that it has a higher damage output on initial impact + it keeps the enemy in place for extra wailing between you and your adc. 2nd it's great in case you and your buddy are surprised if you facecheck your bush late.
Throughout leveling singularity is giving priority over binding, because it has a higher chance of hitting multiple enemy champions and causing a higher amount of sustained AP damage.
If you find that you have someone diving excessively more than they should then you can prioritize the shield over bind if you want but I wouldn't recommend it.
Flash for the ability to run away and close the gap for when lux need's to ignite her passive for that kill she's not in range for.
Exhaust: Well... you are the support and this is a great spell to help you fulfill that purpose esp when the two ADC's on bot go at it.
Ignite: Your ADC should have it so you don't need it. You shouldn't need it if you're supporting.
Clarity: If you manage your AP correctly, the runes and masteries AP regen and the AP regen in doran's rings should sustain you long enough to cause sufficient damage. As your mana pool grows larger throughout the game with items such as RoA, this ability will practically become useless. Plus you can't justify trading this for Exhaust when your ADC dives or you're the only one with exhaust on your team to stop their carry from wrecking everyone. NO!
Teleport: VS flash.... Do you want to be there more often or do you want to be able to do more when you get there?
Clairvoyance: You have singularity..... I guess you could if you really wanted to know where everyone was.
Cleanse: Unless paired with Ghost, you're not getting away. And since you won't be using ghost. No.
The idea of a suppressive support such as Lux in combination with an ADC is to cause more burst damage than can be healed by the enemy.
The trick with this is hitting without being hit. Attack and retreat. Attack and retreat. Until you can burst them into death. That and biding your time till level 6.
Harass the enemy ADC with sparse singularities and binds when you can from bush cover. If the enemy team is using a blitzcrank, it may be better for you to try to land your spells out in the open.
I LOVE Pink Wards for destroying the enemy support wards. Usually after they discover you're using pinks they won't place another ward in river, and you can go back to buying green wards.
When the enemy put's a ward in the bush you're hiding in on bot, PUNISH them the instant they do with a light binding and passive tap. They have to be close enough to put it in your bush. You might as well make them pay for it.
If you're pushing your lane and you don't have a ward use Lux as a ward herself in river bush when you can.
Pushed into your own tower:
This is bad THIS IS BAD!!!! The you're ADC is loosing CS to your tower and the enemie's ADC is becomeing more fed. NOOOOO! Quite simply: Soften up the minions with Lux's Singularity so that your ADC can tap them once to adjust the flow of the lane in your favor.
If you're being pushed back into your tower and your laning buddy is not present, feel free to use your ult and a singularity to wipe out all the minions. They won't risk taking your tower without minions or a lot of team help.
Team Fight Phase:
The flipside to feeding your carry is: Will your ADC carry harder than the enemy's healer can support the entire team, because Lux's late game burst doesn't seem to penetrate as well when the entire enemy team becomes a bit more tanky in general. At this point you should change your play style from damage to prioritizing the protection of your ADC through the use of bind singularity and shield rather than causing the enemy damage outright.
No matter what your play style is, Lux should never be IN the battle at all. She should drop her spells like it's hot and then GTFO until her abilities come off CD. I've had so many people say " WTF lux How come you're not in the fight" to which I respond "Lol Lux isn't a brawler"
WATCH out for of certain patterns of the enemy team's formation:
A closely knit ball or a linear formation of the enemy team is always a good time to drop every ability Lux has simultaneously.
Any champion who have the following types of abilities will wreck Lux:
Are all great combos bot with Lux, because they all have CC and Bursting Ults strong enough to outshine healing abilities.
Malphite, Amumu, and similar ulting champs are always great champions to have in team-fights to help set up lux's combos.
Common Lux Wisdom:
1. Look at your map more than your battle screen.
2. Don't face check when you have Singularity.
3. Save your spells if you fear being ganked heavily.
4. Starting a combo with Lux's ult is always unexpected.
5. If the enemy is juking your bind throw, throw out your shield first. As they dodge your wand, throw out lux's bind in the direction they will juke.
6. Use Lux's laugh. It's both highly enjoyable and obnoxious.
7. Don't be afraid to use Finales Funkeln to push a lane you don't want to over-extend into.
8. Hit every minion in the wave with auto attacks before exploding your singularity to clear the wave all at once.
Secret Maximum Damage Technique: KaameeehaaameeehHAAAAAA
I know it's pretty obvious but I've seen a lot of Lux's that aren't patient with their combos. As a result: they miss an opportunity to ignite a couple of illuminations, and Lux's damage potential is not reached.
COMBO: Stasis -> Singularity -> Autoattack -> Singulairty -> Autoattack -> Finales Funkeln-> Autoattack.
This is a harder combo to pull off, because the enemy will no longer be binded by Light Binding when you ult them. If you can pull it off, I guarantee you the resulting damage will surprise the enemy. Everyone is used to Lux's damage from spells or a couple of illumination ignitions, but not 3 abilities comboed with 3 intermittent illumination ignitions. IF the enemy has used their flash, and you still have exhaust up, it will make your life a lot easier when it comes time to ult. That and your team's extra CC during your ult will help out a lot too.
Now it's important you yell out kamehameha while comboing otherwise maximum damage potential won't be reached in game. ^.^
Stasis --> Singularity --> AutoAttack --> Singularity --> Auto -<==O) Ult -->Auto
Singularity --> Stasis --> Auto --> Singularity --> Ult --> Auto