Hello Guys! I main support and here I will try to guide you on what's right to have on Lux support.Lux is the most hated support because it has potential on Kill Securing.Fear not though we will get you strong wihout needing the help of your ADC.
P.S:Any Questions can be answered at comments,also feedback would be great <3

~Pros:
+Extremely powerful without much AP.
+Can roam successfully with her root and slow.
+Her shields are not weak making her have some useful utility.
+Her ultimate is awesome and doesn't have much CD in the end.
+Dominates Game & Can carry.
+Works well with any jungler.
+Elementalist Squeen

Mana issues fixed

~Cons:
-Performs Poorly against Tanks.
-Immobile.
-If you miss your combo in some situations you can ruin the teamfight or yourself.
-Can't really heal.
-Your ADC hates you.

~Illumination:Illumination is our Passive,it is a very powerful spell that let us poke our enemies down to their doom.It does let us do more auto attack damage with every spell we land.Did you know that Illumination is a great spell that if you get all your spell right it does extra damage? Especially with Ult?..Oh you did? That's great.Be sure though to synchronize your E and R getting them off at the same time lets you do more damage rather than pressing them at a different time.

~Light Binding:Light Binding is our Q,an ability that if we don't have up-we die.Light Binding needs a good decision maker to be its owner;if not used right you are going to be in a difficult position like if you are being hunted down by a Rengar,you should on purpose walk near the bush in order to get the binding off of him,you know he is gonna enter it in order to jump on you.Q is a great spell to assassinate people,by standing out of vision your poor victims won't know where they died from.If you land Light Binding you are bound to be victorious.

~Prismatic Barrier:Prismatic Barrier is our W,Primsatic Barrier a great way for you to poke someone or to protect anyone in your team.You can use it when the enemy has a mage support to get close enough to land your abilities and auto attack them.Careful though-since it travels back slowly you will need to calculate the damage which is going to be done on you.

~Lucent Singularity:Lucent Singularity is our E!The ability that we use more often than any other.Either to poke down or zone our enemies.Try landing your E on the adc when it goes to farm or just have it behind the minions in order to prevent them farming.Our Lucent Singularity is a fearsome and strong spell,since it is AOE and easy to land the enemy will be discouraged and annoyed.Our E is a great way to slow enemeis down and preventing them from killing us.It doesn't have to always be a spell that damages it can save your allies or you too.

~Final Spark:Final Spark is our Final ability and our R.It is the best ability in the game in my opinion.It has a great range and you can snipe any unsuspected enemies off the map.Either when they try to recall or when they think they are safe near a turret.Since we are supports though we can use it for a zoning ult in order to prevent enemies escaping our allies.It doesn't always have to hit in order to be dangerous.

~Sorcerer Boots:Lux is a mage support/AP support-in order to win we need damage-we need to be relevant!Penetration and Speed is important guys don't forget it.I always take this item second.

~Morellonomicon:Morellonomicon is an item which gives you AP/SP/HP and a passive which puts wounds on your target constantly if you hit it with your spells.It gives you an advantage to terminate squishy ADCs or Supports.Also in late game you can pretty much oneshot everyone in the game-of course you have to land your skillshots.

~Liandry's Torment:Liandry's is not very popular on 8.13 the reason is because it doesn't offer as much as Morellonomicon for mages.I'd highly recommend Morellonomicon because in this meta we need power.Everyone seems to do so much damage so we also need that,it is a wise choice against tanks.

~Rabadon's Deathcap:Tremendous AP increase and since it was buffed on the latest patch we are good to go.Rabadon's will remain the best item for any AP champion in my opinion in any patch.It is not necessary for supports however it is not only fun but it is also powerful.

~Luden's Echo:It gives us mana and CDR-it is great for early levels we can stay in lane and poke from afar and we don't have to back because we have mana advantage.Mages are very strong right now and Luden's is a very powerful item.The Proc and our E zones out the enemy from our lane.

~Archangel's Staff:Not in the meta still viable choice though!I do think that it gives a lot AP combined with Luden's however it might be better on a later patch not now.

~Ionian Boots:It gives speed and CDR-although I prefer Sorcerer' Shoes it goes well with Transcendece.

~Twin Shadows:Not a great choice but might be viable in later patch-the AP and CDR is not that bad with Trancedence.Plus the MS.

~Void Staff:Void staff is a great item if you are matched against tanks or enemies who choose to take Magic Resist.It is not necessary on a support however it is very strong and since we go full AP it won't be a difficult decision to make.

~Zhonya's Hourglass:Zhonya's keeps us alive-have it when you face a fearsome assassin like Rengar,he is very strong and he bursts us down easily.

~Boots of Mobility:Boots of Mobility is an item that can boost your speed really much with Celerity.It gives us the chance to roam mid and pick some kills off.Boots of Mobility are not used from Lux players on these recent patches however since we arleady do have so much damage on this patch we should get it for roam and kite power!Plus the AP that we get can help us shield our allies with more power or harm our enemies greatly.

~Athene's Unholy Grail:Athene's is an item that it is "outdated" for AP users.I don't think that's true.Combined with Zhonya's this item can offer a lot tankiness and Mana Regeneration!Since we have damage we can fill it up and heal our allies while fighting.Trust me it does more than you think.Unable for the enemies to finish our allies with an ignite or a Teemo with his mushrooms,even a Darius's bleeds are uselesss!Athene's is a dominating saviour.As I said we can go FULL AP and destroy our enemies but we already have so much damage that we can let our teamates finish them off if we don't oneshoot them.

~Zhonya's Hourglass:Zhonya's is a necessary item when we struggle.The invincibility that it offers and the armor is just what we need in a tough match up.It mainly prevents assassins focusing us and it's a great way to let oursevles get a little bit more tanky.Zhonya's does give us some CDR as well so it is an item that goes well with Transcendce.If you are having a good match-up it is not needed,however it is there when you do.

~ Sorcery ~:
~Summon Aery:Summon Aery is a rune that gives us poke potential in lane-yes it does.Not only able to use it almost every second;our spells and auto attacks become fearsome and annoying to the enemy.Poking them down and preventing them from laning-Aery is a good way for any if not every utility and AP support.Since Lux has a shield combined with Aery it is kind of huge.We rarely let a teamate die in early stages and we are able to turn a fight!

~Arcane Comet:Arcane Comet is a great rune right now! Commonly used by Mid Laners and AP supports this rune gives us so much bully lane potential.Since we root our enemies with Q and slow with E its potential landing is increased and the late damage it does is great four a finishing ult.This guy right here is all you need when you think you lack damage.

~Manaflow Band:With this rune we can poke enemies and gain mana,it is such a great rune.It helps us stay in lane more and it certainly is the way to go.Not only it gives you mana but you can train managing it better.Manaflow Band became a saviour to many support players who had trouble with mana,this rune is great nontheless so it is great to have it.

~Celerity:It gives you 1.5% more speed and since lux has no mobility it is kind of what we need most of the times.It is good for roaming if you roam with her but if not she can escape a little bit easier.I think this rune is strong in every patch so far for utility and AP supports and it has not changed yet.It also gives us adaptive damage,meaning that our AP is going up everytime we are speedy!

~Scorch:Scorch is basically a little weak ignite which is able to pick off kills when someone has low HP.It's a good way to use our full combo with it because most of the times Scorch gets the kill for me in early levels.Think about it,if you can bully your enemy with this bad boy each time you land a skillshot you may force them go back and lose farm.
~Inspiration~:It gives us more AP
~Biscuit Delivery:Biscuit delivery is not very useful this patch-since we don't have any mana problems with my build anyway.However if you struggle in lane that's what you should get.You can stay in lane longer and poke enemies-with trinket you will get more gold and when you go back to your base you will be able to buy a useful item.
~Cosmic Insight:Comsic Insight is a great way for you to get Zhonya's.Combine these two item's CDR and the lowered CDR for every proc item.I think it's a good choice when we get Trancendce-we get more AP potential PLUS we have lower cooldowns which is a very good thing for us.If Lux doesn't have abilities she is nothing more than a scuddle crab.

Magical Footwear:Magical Footwear gives us free boots,between 7 or 10 minutes,if we are not getting Boots of Mobility it is tottaly what you should get.

Domination:It gives us AP.

~Cheap Shot:With our Q and E we deal true damage with our full combo making us very scary for any adc or utility support.It also is a good way to poke and finish enemies while its true damage cannot be protected by armor or magcic resist,so we are sure to deal that much.

~Collective Eyeballs:I like going full damage when I can.AP Lux is very strong right now I'd recommend getting it because you'll get more AP which adds up to damage.I do think it's a little bit off for a support however it works just fine with me.

~Ultimate Hunter:This rune will mostly help you in late game.You will get many chances to snipe enemies and use your ultimate every 23 seconds.Isn't it a great rune?...It is! If you'd like more cooldown on your ultimate you should get this and you won't regret it.

Resolve:Gives us HP and AP.

~Bone Plating:Bone Plating is the number one resolve rune for anyone.This patch especially it has a tremendous effect on our squishiness and prevent us from being killed instantly.It is a good way for you to be safe in lane and actually a good way to trade.You won't lose as much HP as the other support and that is very important for a good laning phase,while you force them back and you'll have vision you'll be able to take the first turret first.It is an ultimate control rune.

~Chrysalis:With more HP and AP,Chrysalis is a way for us to do more damage and live longer.Lux has health issues since her base HP is not that much,however with this we gain a little bit more advantage and we should be able to trade well combined with Bone Plating!

~Revitalize:Revitalize is a rune of a true support Lux.We are not that supportish this time of the season since Lux support is not that strong,that's why we should go AP for now,however it is not bad if you get Athene's as a core item.

As any other champion I will explain why you should get these specific ones.
Flash:Flash is a rune that will let us become stronger,using it to skillfully outplay with our Q combos or either escape in dangerous moments.We should always get flash since we don't have that much of mobility and we should always use it wisely.

Ignite: This spell is very strong lately for its own good.Picking off kills in early levels let you become stronger since the gold that you will get from the kills -will allow you to buy more items getting you ahead.Lux is a mid game champion mostly so Ignite might be the best choice right now-since it gives the early advantage.

Exhaust:Well,exhaust is not commonly used for AP supports-neither from me.I do always feel confident about my Lux after all.However it is a very very useful skill lately-with tanks running only AD items;being stronger than ever...it's a very useful spell in order to survive tough situations and also a great ally on the laning phase.

Heal:Heal is not viable for this patch however just as always the Heal Supp and Barrier ADC combo is a good way to outsmart your enemies.

Barrier:Barrier is a great ally to have in lane.Often ganked from junglers this Spell might save you a lot.It has been so many times that our W was not enough for us because it travels back slowly.Our ADC or teamate might be able to be saved but it happens that many times an ignite is just lethal for us.I'd prefer using barrier against a Rakan or something like a Morgana.

Tips is a general knowledge and that won't change however we can add things.
~Warding,Roaming and Ganking.:Lux is great with mobility boots as we get them first!When you buy the boots do not go at your lane if you see you can pick off a kill on Mid or Top.Lux needs early kills for she wil carry in late game have no fear about that.If you see you can gank your own lane go there as well.I'd recommend you to stick with your jungler and roam,kills is what we need.We have mobility boots therefore we can easily ward the river.Vision Control will make you a very powerful and useful support.As Lux support we have two lanes,Bot and Mid.We must have map awareness as we must see when to move and go mid and not let our ADC die.Lux is not a champion that should win the lane necessarily as if Mid or Bot does well it's pretty much a win.Pressuring other lanes is important as you create distress and you make jungler's job easier.When you wait in a bush for a gank wait for the enemy to do a mistake and then strike,your Q is more deadly that way.

~~Kills:Lux needs kills.Now you might think "Hey we are support! What about the ADC,you are such a noob,lowe elo pls report".Nope that's exactly why we need to secure the kills.We are the support therefore getting mobility boots and roaming to ward with sightstone will get us a huge lead.Our ADC scales well in late game so it will just farm and be fine.So don't worry don't fear to take kills.

~Pressure:Poke the enemy ADC when it goes to farm.Less farm=Bad perfomance.Your ADC has to get ahead,since they won't get OUR kills,you have to spend your mana wisely and of course you have to be careful of your HP and Mana.Don't go there mindlessly,that's why we have to go there when the enemy adc wants to farm,they will need to make a choice,either poke back or get that delicious minion.

~Map Awareness:I promise you that this guide will make you better at your Map Awareness.Since I started using the Mobility Boots-Sightstone tactic I got a lot better at it myself~Ward the river and always have a control ward with you,watch out for the laners and the enemy jungler,where is he? was he top? Mid? Haven't seen him?If you don't see the enemy jungler don't make reckless moves,you have to know where he is.Also when you make a mistake and get caught NO ONE is obligated to help you,you should have had map awareness as where the enemy or your allies were.Never facecheck,your E can give you vision you don't have to facecheck and die.

~Invade:What are you waiting for? First blood! You have ignite and Q,never thought invade if they have a champion like Morgana or Blitzcrank.

~Be Positive:As a Lux main she always say "Be positive"!That's right you have to be positive,no game is won by a stupid toxic Yasuo main! It's won by us with the power of love and friendship,Don't respond at hater comments!You're fabulous and mistakes can happen no one is perfect.Mute toxicity or ignore it.Have in your mind what you need to do and that you must enjoy what you do!Do not flame do not cry just smile and murder them ^_^!

~Be a leader:Shotcalling i a hard task however you should be able to master shotcalling from watching replays and mistakes while playing.It doesn't matter if you are not the best player in the world,just the fact that you can organize your team and do things like a team it is actually a very powerful way to win.Don't force your teamates to listen to you and listen to their complaints however you should let them know when to calm down-when they are angry tell them to take a deep breath.

~Be Calm.:We can't make right decisions when we panic,try to be calm-it's just a game after all right? We can act with logic and wisdom if we are calm and we can shotcall better.Don't get angry on anything-nothing can affect you,if a mistake happens it happens and we cannot change that.We should know where to go from there though-take a deep breathe and make the right decision.

I didn't want to make this guide that long but I just went with the flow!I like making them,simple and hopefully not boring.I wish you good luck and hopefully you enjoyed it and became the best Lux ever~You are great summoner and there's always room for improvement!