Is this OK that I use "doctor (or doctorate) candidate" as appellation on my business card?
Before graduating with an MA (and assuming the BE is a requirement for your current program):

Emma, B.E.
graduate student at University X, program Y

After graduating:

Emma, M.E.

After acceptance into the PhD program:

Emma, M.E.
PhD student at University X, program Y

The exact titles (e.g. M.E. or MA) depend on country and institution.
By the way, I've maybe used four business cards in the last ten years, and I probably might as well not have. (It's nice to read your name on a piece of high-quality cardboard, though.)