After lvl80?

Hi guys,
I've reached lvl80 for the first time in my life, after playing the game periodically (Blood elf, Retribution Paladin if this matters). I haven't played the game for years, but here I am now - not knowing what dafuq should I do xD
I was almost in all greens until recently, now blues. Which is still not okay to unlock the Heroic dungeons so I can upgrade to better gear.

From what I understand, in order to do that, I need better gearscore (~3300/3500), and Item Level around 180 per slot? Here comes my first question:

1. Is this true? And can you help me find working Add-On for this stuff, as I can't calculate it myself obviously? I've successfully installed GearScore and it shows it in-game, which is great, but I can't find anything that works in-game for the Item Level. Tried with TacoTip, SimpleItemLevel, Simple iLevel - nada. The SimpleItemLevels shows that it's installed in-game from the Add-On setting and has options for it, but it simply doesn't work. And for some reason, most of the downloaded Add-Ons, don't work. The game detects them while loggin in, the tick for Load Out Of Date Addons is ticked, but they simply don't work -_-. Any suggestions (and maybe links)?

2. Most important - how the hell can I obtain better gear? From where to start?
What I've done so far is I've gained reputation with the Argent Crusade to Exalted and currently farming for the Ebon Blade. I'm not sure if this is the correct approach tho.
Should I gain reputation with other fractions and which ones? Should I buy something specific from somewhere? I'm asking here, because basically, I find myself in bit of dead end and I don't want to lose time doing the wrong thing.

Thank you in advance!

You can easily enable item levels in-game by pressing ESC to open the menu, go to Interface, click on Display then select "Show Item Level". Its that easy, no addons needed.

You might be installing addons for the wrong version, you should use addons for version 1.12 (or 1.12.1 I think to be exact, not sure).
Get AtlasLoot to be able to see where to get items.

Do 10 games of arena per week, you still get points for losing. It takes 2-3 weeks to get 251 ilvl set item. The actual time it takes to do the games is not that bad but boring to lose and wait for arena points to update but still worth it, especially if you want to do PVP.
Participate in WG battles, 251 ilvl shoulders from marks and some ok other items. Also great honor from WG battles and WG quests, buy pvp items for honor 245-264 ilvl.

PVP gear is not great for PVE so it is not that good if you don't want to do PVP (you didn't say if you want to do PVE or PVP or both) but the high ilvl on it makes it better than the low lvl PVE items you are getting anyway.

For rep you most likely want to do The Sons of Hodir quests but on Icecrown and Frostmourne the bonus rep makes it so you don't actually need to do dailies, just unlock it and I think it gives so much rep that it gets you exalted if I remember right.

You can enter The Forge of Souls, Pit of Saron and Halls of Reflection before you can queue for it by making a party and walking inside. I have been able to multibox (me playing the entire team) The Forge of Souls with a full team of freshly dinged lvl 80s (~2k GS) and after a few runs I did The Forge of Souls heroic so it is not that hard with CC and plenty of people to carry but you need to find people that want to do it and is ok with bringing you with low GS, but might be worth looking if you can find a group.

When you can queue for heroics you want to do it daily for Emblem of Frost which is used to buy good PVE gear and then try to find some VoA group after WG.

You could try to find some ICC rep farm group to get 251-277 ilvl ring (agi version is best for ret paladin).

You can buy some Bind on Equip items like Ring of Rotting Sinew (ilvl 264) and Wodin's Lucky Necklace (ilvl 264), both are ICC thrash drops or some crafted items but they are more expensive (and they have armor penetration on them which isn't great for ret).

If you want to PVE you should look for a PVE guild since it makes it easier to get invited to raids.

You should use my new Addon for average item level (:
http://forum.warmane.com/showthread.php?t=454723

You need avg Ilvl of 180 for HC


You should get atlas loot, then you can see what factions has the items you need, Revered with most of them is not that hard.
-Also look for Head Enchant.

You can also obtain decent gear doing quests to get ready for HC