The Best Meta Gems I Found:
For Melee/Range - Either [Thundering Skyfire Diamond] or [Thundering Skyflare Diamond] They Both Give Considerable Amount Of Haste For 6 Seconds. I Can Only Speak For Skyflare At The Moment This Gives 302 Haste.
For Spell Casters - [Mystical Skyfire Diamond] Is BIS...