If You are in trouble with an AP guy, u can take an Abyssal Scepter. Zhonya's Hourglass is the item with less priority, just not if ure in trouble with an AD guy. Also get Archangel's Staff in the begning of the game, so you wont have the problem of MANA, and you'll get a good AP. Lich bane is the perfect item for Lux, get it in the start and dont forget! If you got sufitient money to buy a Rabadon's Deathcap, get it. You Can Also get Rod of Ages or Rylai's Crystal Scepter if you think you are too much squishy. If you are getting a lot of kills, catch a Meijai's Soulstealer. For Recover Health faster get Will of The ancients, garanting spell vamp.-

In team battles, Lux is very nice and is the queen of area damage. Combinating her damaging spells, is possible to take massive damage to the enemy team. Try using Q+E+R in this order. Her W is good for shielding allies dying for overtime skills, like poison. If You Are Experiencing an 1x1 fight, Lux is not good at all. If the enemy have a great range like caitlyn, tristana or ashe, try to shield yourself in the start, and snipe them with skills from distance, specially with her E. While ulting, if the target is fast or have a teleport or flash, try snarring them with Q first. Ignite is good for damaging invulnerable guys, and for keeping your ultimate, at early game (when the cooldown is high). For carrying turrets, try to spam your skills to get Lich Bane's bonus, so you can get it faster.