Lux is one of the most versatile characters in the game and is extremely useful in nearly any situation, she can poke extremely well if you utilize her passive, she can secure kills with her snare and ultimate and can save her teammates with her shield. This is why i play Lux as often as I can.

Pros: Snare, slow and huge range along with great ap scaling and teamfight skills. Very versatile and in general makes everyone happy. Skill shot based

Cons: Very squishy, skill shot based (can be good or bad), can be counterpicked y common champions such as katarina or kassadin.

Lux's passive is illumination. this skill causes an enemy to take bonus damage from lux's next basic attack after hitting them with a skill and makes her an extremely effective early game poker. however do not feel the need to use it everytime. It isn't worth the extra poke if you miss a few CS however this synergizes well with a lich bane.

Her Q is light binding and can snare up to two opponents dealing damage. one thing to remember is the effect of the spell is cut in half for the second target hit so if trying to combo an enemy champ try to hit them with first to ensure maximum damage. this spell is also great for getting away and is why i wait until fourth item to get boots.

The W is prismatic barrier and will shield lux and any teammates it hits from damage both on the way out and on the way back, effectively absorbing 2 times the damage. this is especially effective in team fights as it can absorb the opponents ultimates to give your team the advantage. It is the reason i dont reccomend barrier.

Her E is lux's main poke tool. it is an area of effect slow and when reactivated it will detonate causing damage to all enemies in the area. this is one of the easiest skillshots in the game and can be used very effectively to zone or poke enemy champions.

Lux's ultimate is Final Spark, a long range wide laser beam of light capable of doing massive damage. this spell is amazing however it can be dodged due to its .5 second charge time in which it shows a red targeting beam. It will also both detonate and reapply lux's passive. this spell works extremely well with cooldown reduction as with 40% its cooldown is around 25 seconds.

Lux's combo is Q, cast E, R, Basic Attack, Detonate E, Basic Attack. If done correctly the champion will be helplessly snared throughout the combo.

So i mainly want to just point out some things. These items are for people who want to carry the game. if you are playing support do not buy these. Now i would like to say if the enemy team tries to initiate on you dont forget your zhonyas!!! this can be an effective way of burning their ultimates while you are untargetable and will take no damage. Also dont forget to sell your morellonomican to buy a final item. Morells is great mid game due to its cheap and relatively high AP and its cooldown reduction however late game you should buy a better item when you can afford it.

Now i would like to clarify my points on the situational items. A liandrys torment is a great item which many peopl will say you must buy. I think there are better items to buy unless your team lacks any champs who can start team fights. the passive an do more damage if you start the fight and if you dont it is nearly useless. now a void staff is great if you are carrying and the other team is trying to build mag resist to counter you. If you arent carrying later in the game and the other team isnt building to counter you, get a lich bane. I get one nearly every game. It works well with lux's passive and has the potential to decimate enemies. On the flip side if an opponent AP is carrying get and abyssal scepter. this gives enormous magic resist.

Always take flash. It is a spell that is great for either escape or securing a kill. I also like to take teleport for extra utility and map mobility. Teleport gives you the option to gank any lane at any time. You could also take ignite and honestly it is mainly dependent on personal preference however the range of smite is smaller than the range of lux's skill so that is why i prefer teleport.

Do not take ghost or heal or clarity or clairvoyance. These spells do not work well with lux. Instead of clairvoyance, buy wards. Instead of heal, buy potions. Instead of ghost get boots and use your slow and snare to even out movement speed. Instead of clarity, well if you use this build correctly you shouldnt run out of mana anyways!

The only other spell i can see an argument for is barrier. This spell is great if the opponent has high burst. However you have a shield so unless you are laning against say a Fizz or katarina this should not be necessary

Lux has a decent strength in laning phase, however she is very mana dependent. to ensure that you can consistently poke down your enemies, try to farm with only auto attacks. Also always try to keep your lane pulled because it is extremely difficult to dive lux due to her cc abilities and can result in zoning your enemy with lucent sigularity.

Generally my main goal in laning phase is to beat my opponent in CS and try not to use to much mana until i am level 6. i then try to slowly poke my enemies down until i am confident that my combo can kill them and then try to land a snare. often my opponents realize this and will go back to gain health. when this happens i am able to outfarm them and gank other lanes.

In my mind mid game begins once one team kills one turret. at this point i like to gank as many lanes as i can. If you can land your snare when ganking you can almost always get a kill or force a flash.

However you have to be careful not to leave your lane unattended for to long. after ganking, unless you are going to try and take a turret, immediately head back to your lane through your jungle. If you go through the river there is a high chance of running into an enemy jungler who will make quick work of squishies like Lux.

One semi advanced tactic i often use with lux is i have my support place a ward in the side bush closest to the enemy turret. when the lane is pulled and Final Spark is up i teleport to that ward and allow for me or my ADC to get a kill in a three on two. this is effective because the other team wont have time to call MIA and will be caught offguard.

The only time i dont gank other lanes is if i am midding against someone like mordekaiser who would quickly tear through my turret. And even in this situation i would try to use the above tactic to help give my bot lane the advantage.

All i have to say in late game is to not travel alone through the jungle unless all enemies are in view. You will die. Lux has high damage output but if she meets someone who can survive or interrupt her burst, she will die, or at least have to flash. What about the snare you say?
At this point in the game most champs will be able to do considerable gamage and have some form of pursuit. whether it be a skill like khazix's jump or an item such as shurelya's.

So stay with your team unless you are at your turret. And even then try to be with your team. In fights, stay back and throw your skills and after detonating your E, then use your Ultimate. This will ensure that your passive can take full affect. If the enemy has an assassin such as khazix, dont forget to use your zhonyas!!!!!! This will not only save you but also will likely result in the death of the enemy assassin.

In summary Lux is a champion that, when used correctly, can decimate enemy teams with her low cooldown ultimate that is also good at picking off any enemies trying to get away. In team fights try to make use of your passive and the active on your items (especially zhonya's). So i will leave in saying go out, and be the brightest carry you can be!