So I bought Lux yesterday after seeing how good she actually is, and I have only lost two games so far, one because my team decided to feed the other two lanes non stop (it happens) and one because our Poppy decided to roam the jungle at level 1 and once he gave first blood, he just happened to get two work phone calls during the match. But, other than those two, I have won every single game, with a very good score. Lux is going to get nerfed soon, so this is your chance to play her before then.
Get improved Ghost, the other Utility talents are straight forward, and in the Offense Tree get the 4 CDR and 3 AP talents, followed with the talent that gives you 15% MPEN
Mp5/lvl Blue and Yellow
Bind > AoE Slow > AoE Slow > Bind > AoE Slow> Ult > Bind, keep alternating, keeping Bind and AoE slow at the same level
Sapphire Crystal x2 HP pots
Catalyst (This is a must, keeps you in the lane forever, makes you able to tank all of the solo tops attacks, more spam = more kills, get this always on your first trip back after you get your kill)
Sorc Boots/Rod of Ages
At this point it is all preference, I either stack AP and change Cata into Rod of Ages, get an Abyssal Scepter, or...maybe Void Staff if you need it
Use Ghost and Ignite, pretty straight forward, Ignite for the extra damage that usually nets most of my kills, Ghost + Bind and AoE slow, it is very hard for them to gank you early game. Just use Q on the jungler coming to gank you. pop Ghost, 450 MS go!
What I usually do is wait til level 3, when I have my slow at a strong point, to start doing the 1 2 punch combo. Just slow them, run up to them, use bind, there goes 1/4th of their hp. At level 6, your opponent should be around half hp from the spam (try not to spam and harass too much, your lane will push and they will recall), use your Slow Bind Ult Ignite and they are dead, usually it's overkill.
That's pretty much it, in all of my games I have ended up with way more CS than the solo mids, and my opponent.