Help me figure this char out

Well, so far i have been enjoying tanking on this character, but just doing normals while im gearing up bit. I searched the forum and the web for info how to gem and reforge my gear to be optimal for tanking. Thing is some say reforge anything I can into mastery, others say to dodge/parry to keep them even. My gemming also needs work. My question is: should i reforge to mastery wherever I can or dodge/parry? Should i be putting pure 40mastery gems into yellow sockets and other sockets that have crappy bonus? Are the 20mastery30stamina gems that I have an abundance of on my gear worthwhile for DKs? And other then some parry, are the red 40str gems worthwhile? Or should I scrap those as well?

I'm a few normals away from getting t12 chest from jp vendor, that should bring my ilevel up to the new heroics. is it a good idea to tank those with minimal Ilevel requirements? Ive done those dungeons a half a dozen times each on dps alts, so I do know them. On normals i have no problems at all holding aggro, and use good sense and addons to know when to maximize DS effectiveness. Just wondering whether the Ilevel of gear is good enough for a DK to tank the new 5 mans.
Sockets:

Red = 20 parry/20 mastery
Blue = 20 mastery/30 stamina
Yellow = 40 mastery

Reforge:
Everything -> Mastery
Pieces that already have mastery, reforge other stat so that Dodge RATING and Parry RATING are withing 100 of each other (if you can, keep dodge slightly higher than Parry).

359 ilvl assuming you have relevant tanking gear is enough to tank the new heroics, though you will have to get used to rotating cooldowns and not facerolling.

Mastery is by far our strongest stat, the reason people want to keep your dodge and parry close together is that they share individual diminishing returns, meaning if you have 2200 Parry Rating and 500 Dodge Rating you have 10.87% Parry (1.58% lost to diminishing returns) and 2.83% Dodge (0% lost to diminishing returns) for a total of 13.7% Avoidance. If you had instead balanced Dodge and Parry Ratings to 1350 of each you would end up with 7.12% Parry (0.52% lost to diminishing returns) and 7.12% Dodge (0.52% lost to diminishing returns) resulting in a total of 14.24% Avoidance (0.54% more than had you just stacked Parry).

The more of either Dodge or Parry that you stack the more extreme the DR difference will be, most people advocate that once you have your Avoidance number (5% Miss + X% Parry + X% Dodge + 4% Swordshattering) close to the 40% Mark that you should try to focus on other stats, as that implies close to 31% raw Dodge and Parry, which will cost significant amounts of stat points suffering from Diminishing Returns to already meet. Don't consider that the amount to strive for, but consider that a sort of artificial soft cap that you probably have too much if you're getting close to that amount.