Not Updated For Current Season
The masteries shown here are not yet updated for the current season, the guide author needs to set up the new masteries. As such, they will be different than the masteries you see in-game.
Lux is an easy-to-play champion with high survivability, low downtime and high damage. She's also cute, isn't she?
This build is focused around AP with a bit of survivability on the side.
Lux's damaging spells charge the target with energy for 6 seconds. Lux's next attack ignites the energy, dealing 20-190 (depending Lux's level (lvl*10+10)) magic damage to the target.
This increases your farming ability and can gain you some kills where the enemy almost escaped. Attack targets your spells have damaged, simple.
Q: Light Binding
Lux releases a sphere of light that immobilizes and deals damage to up to two enemy units for 2 seconds, dealing 50% effect to the 2nd unit struck.
This is your most powerful CC. When laning, it can be used as a damaging spell, but when you are chasing down enemy champions, take care that there is no minions blocking the spell's path.
In group fights, you can shield more champions by moving so that they are in the wand's path.
W: Prismatic Barrier
Lux throws her wand and bends the light around any friendly target it touches, protecting them from enemy damage for 3 seconds.
This is a handy little spell. It can save allied champions as well as yourself, providing great value for mana if it hits on multiple champions. In most games, it won't be necessary to take this to a high level early on if your allies are playing well. If you are feeling particularly squishy, feel free to put points in this earlier than I suggest.
E: Lucent Singularity
Fires an anomaly of twisted light to an area, which slows nearby enemies. Lux can detonate it to damage enemies in the area of effect.
Slow, AoE damage, good. It's not a very powerful spell, but it can help you escape, gain you a small advantage in early game laning and is generally not bad.
Ultimate: Finales Funkeln
After gathering energy, Lux fires a beam of light that deals damage to all targets in the area.
This is a powerful ultimate with a short cooldown. It scales well with AP, and firing it at a champion who is immobilised by Light Binding can take a huge chunk out of their HP.
This allows you to port to your base and get back into lane quickly - more time spent laning equals a higher chance of success
Until level 10 or so you will encounter some mana issues. This helps you stay in lane longer, can give you the opportunity to shield yourself (and others) when you were OOM and allows for a steady damage output.
If you don't like Teleport, you can replace it with Flash for chasing down that enemy who's at 15 HP or Ignite for higher damage output. I wouldn't recommend Ghost or Exhaust as you have plenty of escape mechanics which can also help your allies escape!
Another safe option is Fortify - it's not a brilliant spell, but it won't go to waste unless your team is much better than the enemy in which case it won't matter if you have a more useful spell in that slot or not.
Meki Pendant: This will keep you in your lane longer, and can be upgraded to either one of the mana items of choice.
Mana Potion: This is cheap and will also increase the time you can spend laning; at early levels, it scales really well.
Health Potion: If you think you are going to take some damage early on and want to stay in lane, this will make it safer for the lowest amount of gold for any item in game.
After this, your build depends on the composition of the enemy team.
Magic heavy team (4 or 5 mage type champions)
You should upgrade your Meki Pendant to a Chalice of Harmony. This will keep you in lane almost indefinitely while also providing some protection against the enemy champions' spells.
Next, you buy Boots of Speed. That speed boost is important.
You can then upgrade them to Mercury's Treads to give you that little extra protection against the enemies' magic and decrease the effects of any CC from their team.
Alternatively, if you don't think you need the defensive stats from Mercury's, you can go with Sorcerer's Shoes.
Physical heavy team (4 or 5 physical damage champions)
Upgrade your Meki Pendant to Tear of the Goddess instead; it will enable you to gain more AP earlier, and AP is good.
Next, buy your basic shoes again.
Then upgrade your Tear to an Archangel's Staff -- it will give you a boost in AP early on that makes your ulimate destructive.
Next, upgrade your shoes. You should by now have a feel for the level of skill of the enemy team and buy accordingly -- if you want to focus a little on defence, get Ninja Tabi, otherwise go with Sorcerer's Shoes as they're always a good option.
Get your Tear, Boots, upgrade the Tear to an Archangel's Staff, upgrade your boots -- if there's a lot of CC coming your way, use Mercury's, otherwise Sorcerer's.
From this point onward your build isn't dependent on the enemy team make-up anymore. There are some variations which I will explain.
Which item you choose to buy next depends on how the game is going.
There are four options.
If you aren't prone to dying and forking in many enemy kills, get Meijai's Soulstealer. This should be bought before any items listed below it so that you can build stacks relatively early on.
If you find yourself under magical attack and going down a lot and the enemies seem to be immune against all your spells, buy an Abyssal Scepter.
If you are assaulted by all sort of damage, get Rylai's Crystal Scepter, starting with Giant's Belt.
Otherwise, get a Deathfire Grasp, starting with the Fiendish Codex. Even though the focus is on AP here, a little cooldown reduction can make immobilizing that much easier and insta-killing stuff with lasers more often is never bad.
I usually go with Rylai's and Deathfire Grasp, the order depends on the enemies' firepower. If I still have time after that and am not dying, Mejai's is my next item of choice.
There's only one thing left to do to make you unstoppable once you have bought whichever items of the above four you wanted.
Zhonya's ring! Chances are that the game is over (and won) by the time you get around to buying this, but games can be long.
The main disadvantage of this build is that you don't really provide any useful auras to your teammates.
I'll add some advice on how to play Lux later.
As this isn't finalised yet, any constructive criticism is welcome. It will also be after it's finalised, but it's more important now.