World of warcraft Tanking!?

I have a warrior in WoW currently at level 77 (80 in next few days) and was wondering what to use as enchants and gems when i start collecting good gear. i have a lvl 80 DK dps with tank of spec but never really bothered with tanking with that so that doesn't help me with my question, which is.... Metaphorically if you was to have a Meta gem slot and you had the choice between Stamina, parry, defense rating or dodge rating... in what order would you cl as most important for my char ?