Start with first and third skill because you need to use alone your shield. Been a good lux is play inteligent don't let them kill you always need to have mana for stop them with your first skill.

In team work you will always been behind all and when some enemy champion aproach catch him with your first skill and let all atack him, if more than one enemy champion aproach do the same but use your ult, it have short couldown. You will need some elixir of mana if you want throw one then other and other. Never let your friends alone, protect them and try all still alive

In items you need too much Ability Power for nice and best damage with your skill and fast getting life with your ultimate, it will cause middle life damage or more