All 9 of my bags have Salubrious Chaos Monacles, which have a 50% chance to make something not cost MP. Then I have max Mental Absorb, so anything I kill gives me 50MP for everything I kill. Max Concentrate and Spirit as well.
Spells:
Gravity
Protection
Thunder Head
Blizzard
Rock Press
Also:
Animate Skeleton
Lightning, despite having the best ranged attack, is best when you get in the face of enemies. I dive in and up+attack, or down+attack if I just want to stun (2 uses of down+attack stuns most enemies). I only use the aerial AoE on bosses or situations where I just need enemies to GTFO me. I mostly use up+attack.
I am not afraid to use my spells. If elites come from both sides of the screen, I pop Petrification immediately. Then I burn one down. I am not afraid to recharge MP when there are 1-2 enemies and my skeletons are abound. I often play like a true support, running around stunning enemies with down+attack while my skeletons do the real damage, though I am capable of doing damage just fine.
I have 512 mana, and I refill it. How? Blizzard and Rock Press. Every enemy killed is +50 mana, so against bosses, I maintain my mana by popping these spells against enemies the bosses summon for a free MP drink. Between Salubrious Chaos Monacle and this strategy, I am almost never out of MP. With 7 Thunderhead castings, I keep it going permanently in every single boss battle, increasing my presence when I do have to recharge MP.
When you can keep her running, she's a lot of fun. However, she really appeals to the sort of person who appreciates a strategic approach. My 5 spells provide a nice back of tricks for various situations, and lightning staff stun provides a strong strategic benefit.
Lightning is definitely more difficult at lower levels; you need to tough it out until she becomes more of a whole character. Somewhere