#1 upgrade IMO is the Titansteel Guardian.

After that, I bought:

Hat of Wintry Doom
Chain of Latent Energies
Dark Runic Mantle
Revenant's BP
Revenant's Boots
Windripper Leggings
Ebonweave Gloves
Titanium Spellshock Ring

The rest are quest rewards/drops/rep rewards etc..

I haven't purchased an offhand as the quest reward item I am using (Bulwark of Redemption) isn't that bad. Zom's cackling bulwark is around almost 2k gold on my server and the Emblem of Heroism offhand is better stat-wise (it's not a shield though).

Much of the gear I bought is with future raiding in mind. If you focus on maximizing for heroics the gear in some slots will definitely differ due to the lower spell hit requirements. Although it may seem to be a waste to some people to buy gear, many purchasable items are best in slot until Naxx [and even beyond].

I used Lootrank to help me plan my gear upgrades. The stat weights are from an Elitist Jerks simulation. The weighting for spell hit is rather high so I assume you can adjust that as necessary.

http://www.lootrank.com/wr.asp?Cla=6...k4=0&k5=0&k6=0

The stat weights were taken from:

http://code.google.com/p/simulationc...i/SampleOutput