First of all , the good thing with Lux imo , is the harass. thats why u need the potions, couse ur suppose to harass the **** out of the enemies in ur lane , so u can bind them , and kill them when they are low enough. Or you just make them go back all the time with ur harass.

In this way u can always get good farm on ur lane. And when u get mejias soulstealer , thats were the ganking starts. You want to stack it as early as possible , so if it is good enemies on ur lane , keep harass them til ur lvl 6 (if alrdy arent ^^) and then u can start doing dmg , and getting kills. If u have a hard time , ask the mid champ to help u .

One thing that i think is most important to do with Lux, is to use her own passive , and thats why ur suppose to have luch bane also. That little extra dmg with ur autoattack can do much.

My burst setup is ( I use smartkast so it goes fast ) : Light binding , throwing singluraity under the enemy, Then ulti , then one autoattack. THat autoattack will do dmg , cuz of lich bane , and ur own passive.

And btw , u are harrassing with singularity, but the reason to not specc that one first is beecuz of first blood.

Use clarity so u can harass more , and flash so u can both get away , and get the killing blow if they run away.