Oh hai all :D! Been staring at a lot of builds on here lately that have helped me so much that I'd thought I'd get on my own soap box and throw the knowledge that I've gained at you all. (I apologize for the mistakes I hope to avoid but more than likely will run into being my first guide and all :/)
So many times I've seen a Lux so horrific my soul screamed in agony. And even when they did proper builds, they didn't make use of all her abilities; One of the greatest things you can do with this character is multitask your face off.
Most of all however I hope to just return the favor MobaFire has so often presented to me: tweaking other peoples' ideas with your own talents to make LoL a much more geekgasmic experience.

Flash- is amazing on Lux. Obviously you have the quick get away it provides. The fact that it can pass through walls really messes up a lot of chasers and allows you an almost infinite number of paths so as not to be found when your running for dear sweet life. However, flash if used right can really be an incredible trump card in the lane game. I cannot tell you the number of times I've flashed over a mob of enemies, Light Binded and proceeded to spank someone around for first blood. It's also fantastic when people are just outside the range of your ult running away at such a yummy level of health.

Teleport- is what I prefer to have next on Lux simply because of her nearly unrivaled ability to change the flow of a fight. Let alone going to a lone tower where a minion buffet awaits is always tastier when the turret hugs you back for saving it. One thing worth mentioning about this spell is your ability to back door as this champ (something I'll discuss in detail below). Take for instance when the enemy has a lone tower being stampeded by your minions its so easy to act on your teams luck and crush the tower as quickly as possible.

Advisory Spells

The thing about summoner spells (well play-styles in general :p) is that they are so bound to preference; if you find others useful don't sit here and ham string yourself into someone else's ideals. Plenty of spells are great on this character.

Clarity-Allows you to stay in the lane longer and really helps people who are little trigger happy.
Ghost- Some people prefer this over flash, definitely helps with exhaust a lot better than flash and can be used offensively as well, it's only really lacking with it's element of surprise since the reaction time is so much easier to take.
Ignite- This one is always great for that sliver of health enemies seem to have every now and again when they live through something. Definitely makes you a huge threat early game with such an early game champ.
Exhaust- One of Lux's greatest weaknesses is dealing with a melee dps, this being a counter to that also functions as a veritable ghost.
Clairvoyance- Although it somewhat lessens your combat utility, it turns you into a scout, prevention of ganks and helping your jungler get cheap advantages is always fun; and hilariously so you can use this skill to ult when the opponent is out of sight; however it's really easy to Pavlov someone into getting the hell out of the way when Sauron says hello again and again.

Spells advised against

Heal-This can be useful in certain situations, but usually when you are taking so much damage that you need heal to fix it, there's probably a lot more damage to just burn through the spell anyway: the amount of usefulness other spells have make this one a rather lack luster choice.
Cleanse-Like heal you can definitely see where this can be useful, but nine times out of ten, when your taking damage as Lux its better to escape than to stick around and charge on through with something like this.
Fortify-Yet again this spell is heavily situational. Most of the time when you fortify ESPECIALLY late game, people will just eat through the turret you were trying to save as if the shield was never there in the first place.

Spells I'll shoot you myself if you use

Revive-The cool-down on this thing is nine freaking minutes. And it's only useful if your base is being overrun...do not.
Smite-Your not a jungler, and i don't care how annoying that cannon minion is....no just no.
Rally-Are you an AD character? Nope. Do you want to die a horrible death when you pick this spell? Yes, yes you do :D.

Reds -Magic penetration is benefited most outside of quints with these little cuties. Doubtlessly tanks will forever hate you, and having these really messes a lot of them up early game.

Yellows -Ability power how I love thee xD. Using these in combination with your blues and your quints gives you 46 AP to start the game off: Lucent Singularity will hurt so good that you can harass most champs back to the turret.

Blues -Taking 5 potency keeps the 46 a reality, and the 4 insight backs up the usefulness of your marks.

Quints -46, this will soon be your favorite number.

Contd. -Some people prefer cool downs and mana runes, I honestly do not agree because for one, if you make your skills count, more than half the time your going to not need mana until its futile to stay in the lane any longer. Let alone the moment you get tear of the goddess it will be difficult to exhaust it, and once arch angels blesses you it will be near impossible to do so. Cool-down runes definitely can be useful, but the fact that they are only going to contribute about a second's worth of difference to your basic skills makes them out classed by other runes.

Starting with Lucent Singularity gives you a huge advantage in range, a scout for the bushes, and a decent slow.
Following it up with Light Binding helps more often than Prismatic Barrier would simply because of prevention from 50 damage and yet another escape tool is much more proficient at these early levels.
As you go on Lucent Singularity and Finales Funkeln are going to be your twin nephews that you spoil with attention every chance you get. Yet when they just cant take so much clicking poking Prismatic Barrier Should take priority over Light Binding because its usefulness will increase exponentially over the root mechanic which is the main reason you use Light Binding in the first place.

Starting off with an Amplifying Tome gives you that sexy 46 AP for some harass that will widen some eyes.

Tear of the Goddess Will be your next priority so mana will stop being an issue; I prefer to go for the Sapphire Crystal before the Meki Pendant simply because marginally your going to be using more skills from the raw amount of mana you get from the crystal than the time it would take for your pendant to give you enough mana back.

Kage's Lucky Pick is a crucial item to this build in that it literally allows you to get your next few items faster than you would have without it no matter where you are in the build.

Mejai's Soul Stealer Is your veritable lover. Once you get this item, you obviously have to start being more careful so as not to die. The crucial part about getting this item so early is that you can build Lich Bane while still increasing your AP at a threatening rate. Let alone getting all those stacks early is always nice XD.

Lich Bane is lovely to say the least. It makes Illumination twice as deadly and come end game your going to start cheating on your bookie for the fact that you can do over a K to turrets when most of your items are complete. I've been in several games where this item is the reason our team saw victory. A back door Lux is rather unexpected half the time; so utilizing this surprise in late game when your team is defending easily allows you to clear out a turret and inhibitor before the enemy returns. Just be super careful when doing it again; Pavlov really doesn't like Lux apparently x(.

Archangel's Staff Finishes mana problems and boosts your AP further. Building it now makes room for finishing your build much faster.

Rabadon's Deathcap Turns you into a nuclear weapon. By this point you'll be two or three shotting people.

Deathfire Grasp Will finish things up. The fact that you gain a veritable bonus skill makes her cool downs not much of a problem. Do I even have to mention the amount you'll drool when you shoot one of these things at a tank? Just be sure to hit them when there at max health as much as you can.

Alternate Items

Sometimes the situation will turn sour and you'll have a need for some beef: Rod of Ages should solve this problem for you, however it's rather expensive so you need to use it preemptively if you know that late game is going to be a health contest. But if you need a quick fix just replace your Lich Bane with a Rylai's Crystal Scepter This is a rather good turn around as well since the slow makes Lucent Singularity and Light Binding even more support-tastic. Yet sometimes you'll be doing to well, or people will just find you delicious; either way Zhonya's Hourglass will prevent most gang bangs.

9/0/21. There aren't many other methods to use these properly. Sometimes people prefer to take quickness and let the mana regen drop, but I would beg you to not avoid greed or awareness since that is the worst kind of gap you can have with other players.

Light Binding- This should be used as your opener as much as possible. This skill often goes unnoticed for it's harass potential; the fact that it can go behind a target into another can really make for some safe destruction. Lux is also amazing at supporting allies with escaping: never be afraid to bind and run.

Prismatic Barrier- Is yet another form of support. However this is definitely the hardest skill shot to use perfectly. Always be sure to use the bounce back to full effect. Also know that it can shield your entire team; Lux is the master of cluster wars. And never ever forget that when you are at a stage where mana isn't all that important to worry about, spam this shield like crazy; it prevents a copious amount of harass and can really frustrate isolated damage from characters like Caitlyn and Teemo

Lucent Singularity- Is your primary source of damage and harass as discussed above. One of the best ways to guarantee a hit is to lay this where enemies will run once they know this move is coming; the radius of the hit box supports this style of fire overly well. This skill is also beyond good when the enemy team clusters: a free five man slow and damage bringer is rarely frowned upon. Another thing worth mentioning is when you fire this shot from out of the enemy's sight, they have mili-seconds to process a dodge. The slow on this skill is also what makes it so amazing; fleeing or helping your ally to flee can be made super easy by placing one of these beauties where the chaser's path is sure to go, and always be sure to clip them at the edge just before they leave for maximum effect.

Final Funkeln- <3. This skill is the entire reason I play Lux; The amount of damage this thing gives off is utterly massive. But where it really shines is when the enemy manages to get away with a miniscule amount of health: aim and fire and the opponent will begin to fear pretty red lines. Just be sure to use it this way and not waste it by firing it ever chance you get just to do more damage. Note that just because the enemy leaves your field of vision does not mean you cant hit them; generally you will be able to guess where they will be once your shot fires, so beat them senseless with that fact. The range of this skill is also useful when you're midding: Lux can be an incredible assassin with her precious laser. The number of times someone will turret hug with low health is ridiculous. Use that to your advantage and the number of times you'll be raged at will be just as significant ( you can almost hear Mejai's Soul Stealer squealing in joy). It's also worth pointing out that when you finish your spec that this will do about half or more of a squishy champions health bar; you will be a god with this weapon as long as you pay attention to how much damage the laser will do versus how well your target can take it; this move is at its most useful when it takes a kill since the gap it closes in health is the most significant among your moves.

Illumination- This is the key to maximizing your damage output. Getting these off between spell casts really makes most health bars commit suicide. And be sure to always use this directly after you use Light Binding because unless the enemy has tenacity, your going to have enough time to get a charge off and start another spell guaranteed to hit every single time.

Multi-task

Lux can be a lot like LeBlanc in that button spamming brings you wondrous results: Say for instance your ally is dying but another enemy is begging to be killed running away at low health: simply cast Light Binding at the runaway and Prismatic Barrier your teammate as fast as possible; the time between the two actions when performed as if both simultaneously went off makes you figuratively perform two functions at once. The possibilities with using her skills in rapid succession are endless. My personal favorite is using all three of her damage outputs in a row to make health bars just dissipate.

All in all I hope this gives you ideas for your own psychotic builds and at the very least gives you something to try out when playing this wonderful character. Please let me know before you thumbs down in case I can just fix the reason and please don't be shy to point out a mistake. Hope you all enjoy this build as much as I do and just know that you wont be the only one screaming "IMA FIRIN MAI LAZOR".