I started off by looking at some gear list of what you can get with Justice Points and I started to build my list of what I wanted. Unfortunately, considering the choices available for us, our decisions are relatively straightforward for Justice Points. Also, there are a lot of slots that are not covered by Justice Points. To fill those slots, I looked at the heroic dungeons to find what gear would be the best to fill in those slots.
In terms of what I was looking for in gear, my priorities changed slightly from my level 80 stats. Here are my current level 85 priorities in gear.
Spirit > Hit > Intellect = Spellpower > Haste > Mastery = Critical Strike
A little explanation. The reason I chose spirit over hit is for one major reason. Spirit is automatically converted to hit so it is at the very least equal to hit. However, given the issues that may occur with mana in Cataclysm, we will need to have better mana regeneration out of combat. In this vein, I chose spirit over hit. This also shows the initial priority should be our hit cap, which at level 85 will be *prepare to catch your breath* 1742 to have 17% spell hit. Also, I chose haste over mastery/crit due to the way haste effects the speed our spells are cast and DoTs tick. Mastery and Critical Strike are relatively close in importance. We will want to get plenty of both, but haste is our major stat. What I tended to find with our gear is that haste and mastery were together or crit and mastery were together. When there was a question, I took the haste/mastery. Also, remember that reforging can help to get the gear to where we want it. Finally, and it should go without saying, but leather only to get the leather specialization bonus.
So with all that in mind, here is my ideal level 85 pre-raid gear. I tried to only use Justice Points or gear from heroic 5-mans. Also, I got all this information from Wowpedia, since it is the only one I can access from my job. It doesn't have all the heroic 5-mans bosses' loot, so some heroic 5-man loot may be better than this, however, it has enough info to at least make a starter list.
Head: Cluster of Stars - 2200 Justice Points
Neck: Celadon Pendant - 1650 Justice Points
Shoulder: Somber Shawl - 1650 Justice Points
Back: Solar Wind Cloak (Heroic) - Halls of Origination (H) - Rajh
Chest: Robes of Forgetfullness - 2200 Justice Points
Wrist: Armbands of Change (Heroic) - Blackrock Caverns (H) - Corla
Hands: Blessed Hands of Elune - 1650 Justice Points
Waist: Thatch Eave Vines - 1650 Justice Points
Legs: Leggings of Late Blooms - 2200 Justice Points
Feet: Awakening Footfalls (Heroic) - Halls of Origination (H) - Temple Guardian
Ring 1: Lavishly Jeweled Ring (Heroic) - Deadmines (H) - Admiral Ripsnarl
Ring 2: Rose Quartz Band (Heroic) - Stonecore (H) - Slabhide
Trinket 1: Witching Hourglass (Heroic) - Blackrock Caverns (H) - Ascendant Lord Obsidius
Trinket 2: Tendrils of Burrowing Dark (Heroic) - Stonecore (H) - Ozruk
Main Hand: Scepter of Power (Heroic) - Halls of Origination (H) - Setesh
Off Hand: Apple Bent Bough - Justice Points 950
Idol: Book of Dark Prophecies (Heroic) - Stonecore (H) - High Priestess Azil
So, for only 13,750 Justice Points (Don't worry, this won't be that hard when we are getting 75 justice points for downing heroic 5-man bosses) and a few instance runs, here are the stats that you get.
Critical Strike: 533
Since you are not at the hit cap, you will need to reforge slightly and maybe even gem for a little hit until you get some raiding gear under your belt. If you are going to reforge for your hit, I would work backwards on the list of stats. 40% of the mastery and critical strike numbers come up to 613, so you should be able to find your hit in just those two stats to get to 1742 and still have a good amount of mastery and critical strike.
Finally, if you want to save some Justice Points and go for a sweet staff instead, I would recommend getting Staff of Isolation (Heroic) from Lord Godfrey in Heroic Shadowfang Keep. However, I think the stats would be overall better going with an offhand and main hand due to the increased spellpower of using a main hand/off hand combo.
Of course, when you start raiding, you will want to go for your tier sets and then get the next level gear from there. And you don't need all these pieces to start raiding. From what I have heard, an average iLevel of 340 would be enough to get into starting raids.