Your enchants are pretty much spot-on but your gems are kind of all over the place. Firstly, you probably want the Austere Earthsiege as your meta for most encounters - the magic damage one you have is occasionally useful in certain fights, but your mainspec set should really focus on Effective Health (HP/Stam and Armor) if you plan on tanking anything from Ulduar onward.
Next, you have pretty much no need at all for Crit, so those gems need to go - yellow sockets are almost always best matched by using an Enduring Eye of Zul (+10 Def / +15 Stam) - even after the defense minimum (689 Rating / 540 Skill) as it adds to all avoidance stats plus block. Your red sockets are slightly better, though Parry suffers from a harsher rate of diminishing returns than Dodge, so you should generally gem / enchant for Dodge first.
Specifically, you only gem or enchant for Parry when (character_sheet_dodge% - 10) / (character_sheet_parry% - 10) > 1.88.
So for red sockets where you want the socket bonus, you should use either Dodge/Stam (Regal Dreadstone) or Agility/Stam (Shifting Dreadstone). Dodge offers a little more avoidance point-for-point but Agility offers Dodge, Armor and a little threat and has the benefit of being modified by raid buffs. It's a matter of personal choice more than anything.
Generally you want to put pure +30 Stam gems in every blue socket or other sockets if the socket bonus is undesirable (generally less than +9 Stam).
The Hit Rating makes it good - it's not that Crit is useless so much as that it doesn't add very much and your gems would be better spent elsewhere. Accuracy is a fine choice for threat (if you're beneath the Hit Cap of 8%, of course) and the Crit is just a nice bonus.
As you begin to gear up a little more you may find that you can hold aggro far easier, at which point you may wish to consider switching it out for something focussed on survivability (Major Agility, Mongoose, Blade Ward of Blood Draining) but while you're still gearing up you may struggle to hold aggro against highly-geared DPS so I'd stick with it for now
As for doing dailies etc for gems, don't forget that you can buy uncut gems for Emblems of Heroism (need to trade your Conquest down to Valor then Valor down to Heroism). It costs 10 badges for each secondary colour gem and 20 for the primary colour ones. If you've not got much left to spend your Conquest badges on then this may be a way of doing it that saves you a little cash (or gives you more to spend on flasks, food and repairs anyway :P)
EDIT: The one thing I would say is choose either Dodge or Agility but don't mix and match - if you go for Agility it'll be modified by Blessing of Kings by +10%. The thing with Kings is that the more of something you have, the bigger an increase 10% represents so you'll get more Armor, Dodge and Crit the more you have. Dodge isn't affected by Kings but does give you more avoidance than Agility, generally speaking. As I say, it doesn't matter which way you go down but I would say stick to one type of purple gem.