I would spend them on nothing yet, with exception to Hierlooms. You will need them on the JP gears from the Faction Vendors (You do not need reputation to spend the JP's at them, there is a Master Valor and Justice Vendor out in Townlong Stepps. He is at the Shadopan Temple called Niuzao Temple (Look for Beefy Bison/Oxe) They are located in the Rear of the Temple.
Also you can convert JP's to Honor and buy the Honor 458 Gear at lvl 90. Blizzard kinda did a Normalization on Gear so they are pretty much just as good as 458 PVE Blues. (In fact you can get pieces with Honor you cannot get with Justice points.) These are great slot fillers till 463 gear hits you in Heros.