Really, it's too hard to list the gear options available to you. Your best bet is to champion Argent Crusade whenever you get the chance, and start knocking out instances. Start with the non-heroic instances in your level range, and upgrade to heroics as you feel comfortable. Drak'Tharon would probably be the easiest heroic in my opinion. As you do these over and over, you'll accumulate badges, drops, and reputation rewards. The gear will come. Use Ciderhelm's spec on the front page and you will be fine.
if you reached the 535 defense minimum, i would suggest starting in early heroics immediately. you can gain defense through enchants on your cloak, chest, bracers and/or shield. get the 535--at least!--and then test the waters.
some that i have found to be easier than others (with tank upgrades to look for): H-Utgarde Keep: Unsmashable Heavy Band (ring)
*the Infantry Assault Blade (sword) also drops inside, but i prefer a faster weapon...if you like it, it's there. H-Violet Hold: Bolstered Legplates (legs), Gauntlets of the Water Revenant (gloves) and Lavanthor's Talisman (trinket) H-Culling of Stratholme: Royal Crest of Lordaeron (shield), Legplates of the Infinite Drakonid (legs), Pendant of Nathrezim (neck)
and H-Drak'Tharon is worth a visit no matter how many bosses you are able to drop. The first time i went in Waistguard of the Risen Knight dropped twice.
H-Azjol Nerub offers one of the best tanking belts currently in game
H-Utgarde Pinnacle has a great tanking sword
These are some of the trickier heroics to run but it's based on your groups skill, not yours really. The bosses don't hit hard, and threat isn't much of an issue. If you know a healer and 3 SMART dps, you can do these at your gear level.