Teleport and Clairvoyance works pretty well too, you can teleport to other lanes, and kill them when they have low health. Clairvoyance helps you snipe off people as well

i never used this guide for my Lux build but it is similar to what i made:)
little change on items order:
-tear of goddess 1st(after doloran ofc)
-boots
-catalyst the protector 2nd (or at least ruby crystal, lux is squishy but this is enought HP for mid game)
-soulstealer(as lux you stay behind tank all the time, you shield your teammates, root enemies[protect carry] and pew pew with ult that way you get stacks very fast)

after this RoA (if you die a lot)
and next archangel

thats my idea for lux:) overall +

EDIT
also i would change dmg sequence coz atm you dont need to autoattack to get proc on ult soif target dont die aa him then:)

Tried it out. 1000+ Laser damage at the end was superfun! XD But the cost of the items are slightly expensive, costing about 17k in total. Overall, nice build. +1

has anyone ever thought of throwin in a rageblade and nashors? i go average whole game but as soon as i get rageblade i just rape, your auto attack along with passive makes it quite valuable, just a suggestion people hit me up about i though

great build, i usually struggle with combining rod of ages and majai soulstealer, they dont ever fully reach their potential when i combine them, but thats my play style =) +1 though!

To me this build is better than the one at the Number 1 Spot :3

I like this, especially the descriptions although I prefer to rush tear of the goddess before other items. The way I see it the longer you have it the more mana you will have mid-game.
+1 anyway.

jeez rage again impervious? I agree with him a bit though. It is a good idea to change up the items a bit more for support. I can't think of any items off the top of my head but stuff with auras is usually good. Stacks is just not a good idea if you're support because you're never going to get kills and you will get assists and you are easily killed. Give your team the survivability and support they need while giving yourself survivability too. Mess with it a bit and ill +1 it

AGH NO RAGE WARS PLOX!!!

Rotfl, I don't care that ~30k people have viewed ur build. I'm not talking ****, just expressing my opinion - i find this build better than urs. You don't have to agree or understand it.

@ Dewo , exactly the Truth . Especially the thing with void staff is correct.

But nice guide either way and I would reccomend it instead of the one wich is called " Best AP Carry Guide for Lux or somethin' . " Dont let 'em get you down by downvotes :3 I voted up ( Y )

1st of all i didnt read the comments here so if som1 posted this already sorry.
I am not an expert on this champion either, but you asked for it...

From the begining:
Summoner Spells.
I find Clarity a must have on her. Mana regen sucks at the moment so wouldnt count on it. other thing is Flash. I play her Clarity/Flash, but i think that ppl that are not addicted to Flash as i am, will make a better use of Clarity/Ghost.
2 Escapes are way too much for her imho. She can slow, she can snare, its way more than enaugh to stay safe. Ignite is a bad idea since it forces you to close up on your target, and you should stay in the back as much as possible.

Masteries.
i play 9/0/21 as well BUT.
Utility Mastery is something a MUST HAVE ALWAYS on her. keeping Blue buff with 24% CDR is HUGE for Lux. Other than that, you are missing a Flash mastery eventho you use flash on her. I see you focus on mana here, but if you try the Clarity stuff you will see that it's more usefull than this imho.

Skill odrer.
I use exactly the same setup. I sometimes delay getting the Barrier even later if i feel safe.

Itemisation.
As i use Clarity i want to make as much use of it as possible. That is why i pick Mana crystal as 1st item and spec for Catalyst->Boots->RoA->Soulstealer. That early game survivability is very important. Without that lvl edge you will fall behind realy fast.
Again you are getting tear and staff quite fast. Well... if you swap to Clarity you will have more space for more survival mode like RoA.
Getting Void staff early/mid game is a PURE WASTE. % based penetration sucks monkey balls since it's applied after flat. rushing Ring or Rylai will be a better idea. Buy staff only if you have more than 1 person stacking Mres.

Runes.
I am oldschooler i think but her skill scaling is nice so i play with:
Mpen - M
AP/lvl - S
AP/lvl - G
Flat AP or Mpen -Q

Desc.
Realy nicely written. Good job. Pitty that you post it so fast without proper time of testing. It has something missing but i have no idea what. I see you somehow mastered laning phase and early game and have some problems in mid/lategame, but this is just a thought.

Well you asked for it you got it. :P hope you enjoyed the ride :P