Today I'm gonna give you the cloth blood elf themed set. It can be used either by mage, priest or warlock as there is only one class-specified item - boots, that can be used only by mage, priest and warlock :)
Helm of Arcane Purity
Shoulders - With this one I give you a choice, if you want shoulderpads as in picture above choose Shoulderpads of Knowledge's Pursuit, but if you want something smaller Flarecore Mantle is also a good match for this set.
Chest - Scarlet Sin'dorei Robes
Waist - Girdle of Ruination
Legs - I don't really see the need to transmogrify pants with this set, because they are covered by robe. But if you want to do it despite the fact that they can't be seen Spellstrike Pants have nice blood elf design :)
Feet - Vindicator's Mooncloth Slippers
Hands - Sunfire Handwraps
Wand - Tirisfal Wand of Ascendancy
For other weapons see the leather and mail blood elf sets, you can find there a wide choice of matching weapons.