Which mage class is worth to invest empress set on?

So yeah, i'm mage freak and I love playing mages alot compared to other jobs. Currently i had an I/L, BaM and Luminous. I plan to invest empress set on one of these chars, and i'm not sure which one can benefit empress set the most. I do not own any F/P or BS, so they are out of question. Hence, perhaps anyone who owned them can give me some opinions about whether is i should invest empress set on either I/L, BaM or Lumi.

If any Scanians here, may i know how much empress set excluding weapon roughly cost ? :f6: