Lore:
Born to the prestigious Crownguards, the paragon family of Demacian service, Luxanna was destined for greatness. She grew up as the family's only daughter, and she immediately took to the advanced education and lavish parties required of families as high profile as the Crownguards. As Lux matured, it became clear that she was extraordinarily gifted. She could play tricks that made people believe they had seen things that did not actually exist. She could also hide in plain sight. Somehow, she was able to reverse engineer arcane magical spells after seeing them cast only once. She was hailed as a prodigy, drawing the affections of the Demacian government, military, and citizens alike.

As one of the youngest women to be tested by the College of Magic, she was discovered to possess a unique command over the powers of light. The young Lux viewed this as a great gift, something for her to embrace and use in the name of good. Realizing her unique skills, the Demacian military recruited and trained her in covert operations. She quickly became renowned for her daring achievements; the most dangerous of which found her deep in the chambers of the Noxian High Command. She extracted valuable inside information about the Noxus-Ionian conflict, earning her great favor with Demacians and Ionians alike. However, reconnaissance and surveillance was not for her. A light of her people, Lux's true calling was the League of Legends, where she could follow in her brother's footsteps and unleash her gifts as an inspiration for all of Demacia.

''Her guiding light makes enemies weary, but they should worry most when the light fades.''
-- Garen, The Might of Demacia

This passive is what sets good Lux players from bad Lux players. Choosing to use this passive effectively at correct times will definitely earn you recognition, praises, and a well-earned kill.

An auto attack sets the passive off after any of Lux's damaging skills was used on the champion. You this skill in conjunction with every skill you use in your combo. The auto attack every time you Illumination the person will deal heavy bonus damage apart from your skills.

Tip: Learning to know when to auto attack between skills or just using Lux's skill sets to finish off the champion will result in a good outcome, whether you get the kill or not.

This is your only hard crowd control (Slows don't count as hard). This skill snares two units, whether it is a minion or a champion. Using this effectively can lead to an excellent setup for a fight. Don't just shoot it blindly because it is can easily dodged if the enemy knows Lux.

Tip: Aim to the direction of where you think the enemy will go to try and dodge it.

I max this last because you don't need the extra damage early game or mid game. You deal damage over time through low cooldown spells. Light Binding is used to snare champions in place for Lucent Singularity and Finales Funkeln to deal damage or even to save yourself but to me, this should not be used for mainly damage but rather more for its utility uses.

To me, this is what I consider essential for Lux as a behind-the-scenes caster. This skill shoots out her wand and gives a shield to any champion in range TWICE. This saves countless lives and could even help win team fights.

Because I play Lux as a spammable caster, this skill is the most used skill in every match I play. Shoot this out to protect damage from minions, from champions during fights/ganks, and even help protect the one taking agro from towers and significant monsters (baron/dragon).

Tip: Use this when you know that your team is grouped up and about to go in for a team fight. Save carries unless some significant other is more important.

I max this second because after Lucent Singularity is maxed for damage, this is for team fights that happen during mid game to help keep other carries/tanks alive. This, in my opinion, is more preferable to max before Light Binding.

This skill is your main damage early game and used to reveal hidden areas. It requires a decent amount of mana to use so conserve mana unless you need to use it.
Don't rely on the slow since it isn't that big of a deal but it still is helpful.

Tip: Aim a little behind the enemy if you know they will run back from seeing you use your skill and explode right away.

I max this first because it is a great source of damage early game. Its range is good for a skill that does insane damage when maxed first.

This, after level 6, is your main finisher skill, farming tool, relic/baron/dragon stealing laser, poker, and is Lux's long light "stick". Don't be afraid to use this because its cooldown is extremely low even without items. This is why most people play Lux for.

Tip: After level 16, you should have both Chalice of Harmony and Athene's Unholy Grail and plus the mastery Arcane Knowledge will give you a total of 34% CDR and because of this, Lux is able to minion wipe a mid lane every 30 seconds with a cooldown of 26 seconds on her ult. Spam this as a way to revealing areas or to steal baron with Lucent Singularity as a tool for vision.

Obviously I max this whenever possible because this is Lux's signature move and that it increases its damage and lower its cooldown.