would be having her lower tier skills, Diva, Quickslayer and Slayer maxed (but increasing each skill every other slot, so it can be spread out as you go on). Inner Glow, Hit and Run and Enforcer are some important skills on the 2nd tier. Inner Glow haves you gain Health when you phase walk. Enforcer increases fire rate when you kill somebody and Hit and Run increases melee and phasewalk duration (I use it more for phasewalk duration then melee). Hard to Get, Diva, Inuition and High Velocity are something to look at and for the final tier Mind Games and Phoenix are your best friends. I know this is alot of info to take in, but checking out one of these builds will help some.
http://borderlandsthegame.com/skilltree/lilith/#21522000050500515055500 I've changed Lilith so many times and SMG/Elemental weapons really make her unstoppable. I wish I knew that at the beginning, because I rarely used them, but now my profiencey is at 50 with just playing the newest dlc and its still fun as hell.