Wyrmrest is a good choice for starter tank gear. Check out what they have to offer...
[Cloak of Peaceful Resolutions][Breastplate of the Solemn Council][Sabatons of Draconic Vigor]If you already have better crafted gear or dungeon drops, then go for
Argent Crusade because they have the head enchant you need as well as some starter tank legs you might want...
[Arcanum of the Stalwart Protector][Special Issue Legplates]Kirin Tor has some epic gloves, though the heroic badge gloves are probably better...
[Fireproven Gauntlets]Ebon Blade has some starter boots...
[Toxin-Tempered Sabatons]Here's some info from
How To Tankadin At Level 80...
If you wear one of the four faction tabards below while running a level 80 5-man dungeon on normal, or ANY Northrend 5-man dungeon on heroic, you will gain reputation for that faction for every monster you kill.
[Tabard of the Wyrmrest Accord][Tabard of the Argent Crusade][Tabard of the Kirin Tor][Tabard of the Ebon Blade]This is called Championing...
http://www.wowwiki.com/ChampioningThe level 80 5-man dungeons are:
Culling of Stratholme
Oculus
Halls of Lighting
Utgarde Pinnacle
I think that the hardest to grind reputation with is Wyrmrest accord, since while there are quest chains that give rep, there are only 3 dailes, one in Dragonblight, the other two in Coldarra, and one is a MAJOR pain in the butt. More info...
http://www.wowwiki.com/Wyrmrest_AccordNext most difficult is the Kirin Tor, since the only dailies that give rep with them are cooking, fishing, jewelcrafting, and the dungeon dailies. There's also 4 small quest chains that give Kirin Tor rep. More info...
http://www.wowwiki.com/Kirin_Tor Argent Crusade and Ebon blade are about equal in terms of grinding out the reputation with dailies. I'd wear those tabards last unless you're working for a specific reputation reward. More info...
http://www.wowwiki.com/Argent_crusadehttp://www.wowwiki.com/Ebon_Blade