Hi, Hello and thx for wasting Ur time for my guide ;] and big soz for my Eng ;]

1st and most important, Lux is rly squishy, so U should stay on back line.
2nd. Don't die.
3rd. Don't waste sumoners skills if U can use Clairvoyance to help lines, do it.
4th. Trye get mid, if U do, gank lines after 6 lvl its easy.
5th. Harass, harass, harass and after 6 kill with laser :D

I post here my runes, they work for me, cos I don't need mana regen cause of clarity spell, I don't need hp runes cos I don't let enemies to harrase me, I don't use CDR runes, cos Mejai' and Morello's give a lot of CDR.

I need to mark fact that after I get Zhonya's Hourglass, I'm selling Doran's ring and making Archangel Stuff.

About skill sequence, PCIK "Light Binding" as first skill, it's helpfull in case of ganks. Remember U are squishy.

Clarity for MP.
Clairvoyance for effective use ulti.
U can also take flash instead of Clairvoyance if U need it ;D

Don't die. Get stacks. Trye to get Blue Buff anytime U can.