Well, in my lol history (4 years) i always loved the Lux playstyle, but i wasnt good at midlane.
So as a support, first i tried Orianna and Taliyah, and they were good, but i was feeling something missing.
A little bit later i learned how to build, so i come back to Lux, this time as a support
AND OH MY GOD
THIS
SHIELD
Lux have the biggest supports shield, but her shield dont apply any buff. Everyone says: Morgana's Black Sheield is better, yeah, it is good. But Lux shield is the ''pure shield''
With Aery her shield can be with 150 of resistence in the first level, and can go to 360 (pure, without AP)
With AP can go to 600!

Lux can be very helpful for her team, but she is squishy.

Lux can do a lot of demage and poke, but she is full of skillshots.

Lux can be a box full of poke, but she cant escape.

Her Q can catch two, and you can use this for your advantage in lane, launching in one minion to catch a champion, they never expect that.

Her E can give a huge poke, but you also can let it on the ground to apply 45% slow, it can save lifes, or leave them.

Her shield is a whole team shield, so you ALWAYS need to be in bacwards, throwing it to catch the most champions that you can.

In this runes you turn your Lux into a demage Janna
You can:
Make your shield 50-130 better on Aery
Have a sustain in lane phase with Manaflow Band
Gain CDR and AP with Transcendence
Turn your shield into a secondary health bar in mid-late game in Gathering Storm
Heal your allies in your CCs with Font of Life
And make your shield and heals better with Revitalize

Passive: Illumination: Lux's offensive abilities mark all affected enemies with light energy for 6 seconds.
Her basic attacks and Final Spark Final Spark consume the mark, dealing 20 - 190 (based on level) (+ 20% AP) bonus magic damage.

Q:
Light Binding TARGET RANGE: 1175 SPEED: 1200 COST: 50 / 55 / 60 / 65 / 70 MANA COOLDOWN: 13 / 12.5 / 12 / 11.5 / 11
Light Binding
ACTIVE: Lux releases a sphere of light in a line that deals magic damage to the first two enemies hit and Root icon roots them for 2 seconds.

MAGIC DAMAGE:
50 / 100 / 150 / 200 / 250 (+ 70% AP)

W:
Prismatic Barrier TARGET RANGE: 1075 SPEED: 1400 COST: 60 MANA COOLDOWN: 14 / 13 / 12 / 11 / 10
Prismatic Barrier
ACTIVE: Lux launches her wand in the target direction, which then returns to her after reaching maximum range. Allied champions in its path are shielded for 3 seconds, which stacks on subsequent applications.

SHIELD STRENGTH:
50 / 65 / 80 / 95 / 110 (+ 20% AP)
If Lux shields at least one other ally on the outgoing path, the returning wand will grant twice as much shield.

EMPOWERED SHIELD:
100 / 130 / 160 / 190 / 220 (+ 40% AP)

E:
Lucent Singularity TARGET RANGE: 1000 EFFECT RADIUS: 350 SPEED: 1300 COST: 70 / 85 / 100 / 115 / 130 MANA COOLDOWN: 10
Lucent Singularity
ACTIVE: Lux sends an anomaly of twisted light to the target area, Slow icon slowing nearby enemies and granting Sight icon sight of the area around it for up to 5 seconds.

SLOW:
25 / 30 / 35 / 40 / 45%
At the end of the duration or if Lucent Singularity is activated again, the singularity detonates, dealing magic damage to all enemies in the area.
MAGIC DAMAGE:
60 / 105 / 150 / 195 / 240 (+ 60% AP)

R:Final Spark TARGET RANGE: 3340 COST: 100 MANA COOLDOWN: 80 / 65 / 50
Final Spark
ACTIVE: After gathering energy for 1 second, Lux fires a giant laser in a line that deals magic damage to all enemies hit, briefly Sight icon revealing them as well as the surrounding area.

MAGIC DAMAGE:
300 / 400 / 500 (+ 75% AP)
If Final Spark kills at least one enemy champion, a percentage of its remaining cooldown is refunded.

COOLDOWN REFUND:
10 / 30 / 50%