You are unfortunately logged out in dps and/or pvp gear so I cant comment specifically on you tank gear but I can give you some hints on gemming in general so it might apply to your other gear also:
1. Never use AP gems (they dont scale with buffs like BoK)
2. Its very seldom a good idea to stricly gem for the socket bonus. For tanks Stam gems are the way to go most of the times for tanking (no matter what the socket color is) and Strength gems are the gems to use for DPS (for DKs and some other classes.
3. Use epic gems. Your gear is very low so far so I understand not using them so much yet.
4. Enchant all your gear. You might not want to use the best ones yet if you are emblem grinding for vendor gear but at least use one of the cheaper enchants then instead.
Comment about 1: There is always an ongoing debate about Stam vs Avoidance but most tanks gem/enchant for Stam.
Comment about 2: This is after you have reached the "caps" you need (for example minimum 540 def and maybe 263 hit and 26 exp a little depending on you spec)
Other than that your professions arent the best unfortunately. JC/BS or JC/Ench are the ones I think I best (because of the extra stats they both can give).