Hello, and welcome to my Lux guide. This is my take on Lux ever since I was a wee level 10 in the league I've been playing Lux if I ever go mid, I have also pick lux to counter top lanes such as vlad, she actually works great top although many would look down on this, but you know you just have to start that new meta.

Marks
Greater Mark of Insight - You're AP
Seals
Greater Seal of Clarity - Lux loves mana.

Greater Seal of Force - Yay! Damage.

Greater Seal of Replenishment - Alternative to Clarity runes. ( I prefer these ones)

Glyphs
Grater Glyph of Force - Ap op

Quintessence
Greater Quintessence of Potency - Early ap :D

Greater Quintessence of Force - Scaling ap :D ( I Prefer These )

Good Choices

Flash
Great escape tool,engage tool - top pick for any Champion. (very few exceptions like Olaf :D)

Teleport
I love this spell, but it's been so underrated Lately - Ganking other lanes, getting back to lane faster.

Okay Choices

Ignite
This is great if you want to win lane but other than that it's a bit useless on lux -
more damage in lane, out of lane not to great of a choice for lux

Heal
If you don't know what backing is, or the opposing summoner has "A LOT" of harass - overall not a bad choice but there is better. (you are also lux so you shouldnt be to close team in team fights)

Cleanse
Good if they have alot of CC and you get caught out. - same as heal

Clarity
Yay Mana - this becomes useless very fast - ok if you have no mana runes or you love spamming constant spells for no apparent reason.

The Rest Don't Deserve a Section.

You may ask why I level what i do first, It's going to should something like "BUT WHY D':!!!".
Well just keep reading.

Light Binding
I level this skill last, are you still asking "BUT WHY D':!!!". well yeah it dose pretty good damage, but the cd only goes down by 1 second each level and the snare is the same every level, you will say "BUT PRISMATIC BARRIER ONLY GOES DOWN BY 1 SECOND TOO D':!!!". well I'll explain later.

Prismatic Barrier
Okay, I level this spell second "BUT WH...", omg shut up and listen, this spell is just amazing a multi-target shield sooooo op, you'll be able to give your whole team a 200 damage shield by level 12 which is when you should start team fighting more often, this is a team game don't go lone wolfing it up out there.

Lucent Singularity
This is your major damage spell, it slows, it's aoe and it has amazing range this spell can get down to a 6 second cd if the .1 extra second makes you so mad you could punch kittens from our 39% cdr then get 1 glyph of celerity.

Final Spark
This is what makes lux.. lux Spam this spell ever time it's up i use this to force opposing summoners our of lane or just even clear with it, if you know/think they enemy team will go for dragon/baron Lucent singularity for vision, and final spark (use lucent singularity before final spark, due to final spark proc's lux's passive for more damage.)

OMFG SHIELD OP!
(and remember Kill Steals don't exist.)

21/0/9
Extra Damage, Extra Kills, Extra wins :D.