Welcome to my very first guide with the very first Champion I've ever played, Lux! I have played many games with Lux ever since I started playing League of Legends. I am currently unranked as I don't really play Ranked much but from time to time I do.

This guide is how I play Lux so if you feel the need to downvote please don't.

[Update] I've recently noticed that my build and ability sequence is very similiar to other builds, but that's how we Lux player's roll.

Standard 21/0/9 AP masteries. Putting a point in Summoner's Wrath instead of the third point in Havoc is much more beneficial because 5 AD/AP is stronger than an extra .66% increased damage.

I get Greater Mark of Magic Penetration because of Lux's AP characteristics.
Greater Seal of Scaling Magic Resist because you will be fighting other AP Champions in Mid.
And finally, Greater Glyph of Ability Power and Greater Quintessence of Ability Power for Lux to be stronger.

Total Price: 14'145 IP

Illumintaion (Passive)

Lux's damaging spells charge any enemies with energy for 6 seconds. Lux's autoattacks or Final Spark will ignite the energy, dealing 10 + (10 x level) magic damage to the target.

This passive becomes your poke and harass just from a simple basic attack. It helps you farm minions fast and gives you a headstart on level to dominate your opponent.

Light Binding (Q)

Lux releases a sphere of light in a line, dealing magic damage to the first enemy it touches and half that damage to a second nearby unit. Additionally, the first unit struck is bound for 2 seconds, and the second unit for 1 second.

This skill is what starts your combo's or a perfect [[Final Spark]. It stops an enemy from running away and also lets you cleanly disengage.

Prismatic Barrier (W)

Lux shields herself for up to 3 seconds and throws out her wand to a target location, applying the same shield to friendly champions in its path. Her wand then returns to her, again shielding friendly champions and Lux herself upon touching it.

One of the BEST shields in the game. It's basically 2 shields in 1 (If you aim it right). Use this skill to help your team engage in a teamfight so they can take a deal of damage without losing much health. Since it has an initial shield then comes back and refreshes itself, it can help with moves like Ignite and Toxic Shot.

Lucent Singularity (E)

Lux sends an anomaly of twisted light to a target area, revealing it and slowing enemies within for up to 5 seconds. At the end of the duration or if Lucent Singularity is activated again, the zone will detonate and deal magic damage to enemies in the area.

This ability is your main source of damage and when utilized with Illumination the damage can be devastating! Apart from using it for damage, I use it to catch up to running Champions. Lucent Singularity in front of the Champion to slow him/her, Light Binding to Snare them, then Basic Attack, Detonate Lucent Singularity then Basic Attack. Easy Kills.

Final Spark (R)

After gathering energy for half a second, Lux will fire a broad and long-range beam of light in a line that will instantly deal magic damage to all enemies in the area. Any enemies that already have the Illumination debuff have it ignited for magic damage, then re-applied.

Lux's Ult is semi-global so it can catch a low health Champion from far away! Try to save it until the enemy Champion is low for and always keep track of the Enemy Champions HP and the damage Final Spark does for a guarenteed kill.

When you spawn, Crystalline Flask and 3 Health Potions are standard. Always remember to buy Sight Wards to prevent yourself from getting ganked
Stay in lane long enough to afford Sorcerer's Shoes (or just Boots and Chalice of Harmony.
Take Athene's Unholy Grail before Rabadon's Deathcap because it will give you better mana management and in this time of game (Early-Mid) you don't need to harass just farm / poke.
Then buy Zhonya's Hourglass for the extra AP and armor, also for the active which WILL save your life if you're getting dived etc.
After that buy a Void Staff for the Magic Penetration and AP + a Lich Bane for the passive and AP (Additional Mana and Movement Speed is always good).
For Boot Enchantments choose: Alacrity for the +15 Movement, Homeguard to defend your base / get back in the fight, or Distortion for the Cooldown on your Flash (It takes off around 1 Minute).

TL;DR
Buy AP, Magic Penetration and Cooldown Reduction Items.

I know some other Lux build's are better than mine but I really tried on this one. I'm not really good in making things like this but I really hope it is good. This isn't an in-depth guide just one that you click, read and use. Please give me a good rating :)
I will keep updating if there is ever a new patch/update.

Eximai