Summoners War: Chronicles

In short, Lulu should be tanky (High HP, DEF) including good resistance & evasion. 

Ideally from Early-Game → End-Game rune slots 2/4/6 is commonly HP% or DEF%. The sub-stats to those runes should also include RES%, EVA% as well as more HP% or DEF% (Flat versions can work as well depending on where you are at in the game). The type of runes you should use is also commonly Energy / Defence / Foresight or Endure Runes. 

Books and Galaxy stones should be what you're lacking (e.g. If you think you need more DEF, add a DEF% book or Stone)