If you're having an issue with a skill shot champ (which Lux is pretty much one), try someone else. There are others you can pick that could melt faces. When I Mid I usually play Lux, Ziggs, or Final Boss Veigar. Only reason I can play skill shot champs well is cause of my main, Jinx. I had to learn how to land those W -Zap. After that I started using more skill shot champs like Morg and Thresh when I support, which amped my accuracy. It takes practice and accuracy.
Also remember, League isn't always about getting the kill. If you got one, great! But even if they had to retreat and recall, that's still bonus points. Why? You've forced em outa lane to heal. That's gold and XP they are loosing out on.