Rune Choices
Theres really not much here thats not self explanitory, Magic Pen runes i find are good for any burst/casters.
I've chosen Mana P/Level for the build because they will help more late game, but personally i prefer Static mana runes, just for that extra bit of lane survivability early on in game (by not having to recall for mana)
However i have chose static Ability Power runes over the P/Level runes yet again for the little boost of power early game, just to make lux a little less useless in the first 3/4 levels of the game.

Summoner Spells
I take Ghost and Flash every time as Lux just to make myself a little less easy to kill and having flash really helps with lining up Lux's Death laser ult.
NOT taking clarity is a bit of a risk i'll admit as sometimes you may find yourself running out of mana pretty quickly in early levels but i tend to just rely on a team mate having clarity, or just conserving mana and not wasting it.

Gameplay
Lux is great both mid and laning. I prefer to play her in a lane just because i think having a disable in a lane is a great advantage, expecially since lux's stun can hit two players, which is great offensively and defensively.
I play Lux pretty agressively early game, and try to really harrass the opponents out of XP range just to get the levels advantage from them. because of this I don't tend to take the shield spell until a bit later on where it comes in handy if i end up getting a bit cocky and try to go for silly kills (Another reason why i don't take it is because it has the worst AP ratio out of all her spells).

Items
I start off with dorans ring mainly for the 120+Hp more than anything else, the 10AP is a bonus and so is the mana regen but Lux really needs that 120HP early game.
Sorcerers shoes, self explanatory when playing a caster.
Archangels staff(s).....I think having at least one, if not two of these end game for Lux is essential. If you get Tear of the Godess as quick as you can, You'll find yourself with a big enough mana pool to benefit from having an archangels staff as soon as you get it..I Usually end up having 130AP just with Archangels and Dorans ring (inc runes).
If you're able to not die, Soulstealer is just brilliant, 20 stacks is really easy to get and even easier to keep if you're good at using flash. the 15% CDR from 20 stacks is also brilliant, leaving you with a 26sec cooldown on your ult at level 16.
Zhonyas ring boosts the above stats by a lot and you should find yourself with about 500AP by the time you can afford it, making your laser a brilliant fight initiator and ender at this point.
I've chosen another archangel just for a boost in AP, that and i've never really tried anything else as her as i've never needed to.
Lich Bane is pretty wierd i'll admit, but If the game lasts long enough, this, combined with your illumination passive will deal about 1400-1500 (i think) damage just from a basic effect, and can bring down a tower/inhib in a matter of seconds.
i have experimented with Buying Nashors tooth or some kind of CDR item instead of the 2nd archangel, but It didn't really work out, So for me, the final 6 item set (if you ever get that far) would probably be..
Sorcerers Shoes
Archangel Staff
Archangel Staff
Mejai's Soulstealer
Deathcap
Lich Bane.


Proof it Works?
Heres a couple of screenshots taken from my last 20 or so Games as lux, admittedly they are all Normal games and Not ranked, but I'm too scared to play Ranked alone and mostly my friends just play normal games so i play with them.



This is my first build on, so comments or suggestions are appreciated.