Meta gem: Stamina + armor value
Red gem: Parry + mastery
Blue gem: Mastery + stamina
Expertise is way too much - 19 is enough and I have seen DK tank with even less but its more how are u comfortable with
Reforge parry to Dodge (to keep as close them as possible because parry comes from strength too). Use DK weapon enchant Shordshattering as it adds 4% parry which at starting gear is pretty huge boost. Reforge expertise to Mastery or hit (depends on Your play stile, I would choose mastery). DK is most sensitive tank on player skill as its based on Blood Shield and loads of CoolDowns.