This may not be the most refined build ever for the Lux Champion. However, I am quite successful with it.
Skill Sequence and usage
The most obvious thing about the sequence is that I do not skill PB (W) until Lvl 13. Imo, it is far more important to max LS (E) asap, followed by the other attacking/ stunning skill LB (Q). Also, I find PB more effective in the late game. When in team fights, it is crucial to cast PB in a way, so that most of your team mates, if not your entire party gets shielded - obviously.
Ultimate (Finales Funkeln)
My favourite thing about Lux is her ultimate. FF (which is German and means 'Final Sparkle'). Be sure to use it very frequently. If pressure on a turret gets too high and minions are involved, I port in and use it to clear the entire wave (preferrably when they are moving and still in one line). Finish the remaining monions of with your passive. Also it is highly effective to keep away enemy champions from engaging targets since they usually back off when hit.
Be sneaky! Since the range of FF is quite long it is highly effective to shoot it out of the fog of war. Enemies do not see your positioning and are less likely to react to/ dodge it. I do most my kills by DPSing foes to around 30% health, then pulling back and finishing them off with FF.
Against squishy targets, this is usually a guanteed kill. Positions yourself well (bush or FOW)
Stun with LB -> before auto attacking and triggering the passive cast LS in front of the target -> trigger passive and pop LS asap -> trigger passive again -> finish with FF (if target is not dead, blink in and trigger the passive applied by FF). That should do it. Depending on your summoner spells you can also ignite etc.