Not Updated For Current Season
The masteries shown here are not yet updated for the current season, the guide author needs to set up the new masteries. As such, they will be different than the masteries you see in-game.
Lux by definition is a support character, but she can be as deadly as she is supportive.
This AP works well when you want to harass your opponents and score big kills. When playing Lux, be sure you are laning with a tank or pretty dependent champion that can help take some damage for the team. When in play be sure to always stay in the bushes to help keep away the pesty minions. If well fed you can easily 1v1 sometimes 1v2 ,but thats only if you are well built and you have the balls to do so. Just remember you are fragile and can break very easily. But it's also a good idea to deceive your opponents that way to lead them to their death.
As a start off item, always go with doran's ring. It will give you a little extra hp and start you off with a little AP and mana regen.
If harassing is going well and you scored a kill or two start working for your sorcerer's shoes and Meji's Soulstealer. Get the amplifying Tome and the Boots of speed to start off with. Personally I would get the soul stealer first then the shoes so that I know the next kill i get will add some AP.
If harassing isn't going well try leaning towards the more supportive lux and help out your partner with some assists. Work toward the shoes as well but instead of soul stealer go with rod of ages or something that will keep you in the game longer.
But this is a harassing lux build not supportive. So, once you have the soul stealer and the shoes, it should be getting close to mid game or you are in mid game. Start working toward Zhonya's ring by getting the large rod first to really do some damage. Once in mid game start roaming with your teammates to start ganking the lanes and jungle.
From mid to late game, if you have been getting kills and your stacks are high and you have the ring, you should be dealing fatal amounts of damage to your opponents. If you want to add on a little more AP just for laughs and giggles go with the rod of ages. Other wise work toward some armor. I personally go for the frozen heart because the glacial shroud gives you some ability cool down that can help you reload your rainbows and fire more frequently.
With the skills portion its fairly easy. For starters, the first skill is really up to you. I personally take Lucent Singularity right away so I can farm minions and keep away opposing champions from getting close. Next get Light Binding right away so you can trap your opponents and then hit them with Lucent Singularity. Light Binding will also give time for your lane partner to get in some hits before they retreat to the turret.
With the constant harassment, your opponents are going to stick by the turrets a little more so back off just a bit so they can come out to play. Situate yourself so you can bind them. DON'T use Lucent Singularity right away just deal physical attacks to start and as soon as the binding is about to give cast "E" between your opponents and their turret. They will walk right into it slowing them down so you can get in a little more physical hits, and then ignite your spell to deal even more damage.
Now Lux's passive is a deal breaker. Light energy stores up on a unit when they have been hit by a spell, and the next physical attack Lux does ignites that energy and deals bonus damage. If you harass them correctly that passive will end your enemy. BUT the passive only lasts 6 seconds so be sure to hit them quick before it runs out. If you have to run next to the turret to do so then do it. A kill is definitely worth a little damage, but don't be greedy if you have low health to begin with.
Level 6 is a lucky number for Lux. Once level 6 there is no more sacrificing health to finish an opponent. Better yet you can finish them much faster even if they have a 3rd of their health. Lux's rainbow ult is definitely the most useful skill she has. It does take some time to master the skill shot but it's worth every kill. If your teammates can't keep up with the running opponent to finish the job, lend them a helping hand...or rainbow. Some teammates might get mad at you for Kill stealing but it's their fault if they couldn't finish the job. Another thing to remember is to always shoot multiple enemies if possible, assists count as stacks too.
When using Lux's ult, always run to the opposite wall of your opponent and angle your shot toward them so they have to run into the rainbow's path. Now if you are playing some champions who aren't so smart as to dodge when they see the red light, by all means shoot right down the lane to finish them. Doing this will even farm some minions who didn't even make it to battle yet.
In the late game, when your AP is off the charts and your Ult is very powerful, it is a good time (again) to get glacial shroud. This will give you a little armor and a 20% cool down for your abilities making your powerful rainbow into a frequent powerful rainbow.
Remember!!! ALWAYS USE THE BUDDY SYSTEM!! While you might have fatal spells at your finger tips, you do not have the proper protection. Getting killed won't help your stacks very much. Neither will it help your team.
ALWAYS know your MIAS. Though you are harassing, you don't want to dig yourself into a trap leaving you helpless. So be sure to stay very cautious when pushing and harassing.