Build GuideMirrorball is the absolute requirement, without it the first skill choice is obsolete. Make sure to check out zirkaloy's comments below for alternatives, especially if you don't have Mirrorball (use Spectral Blade - Flame Blades)!
Prioritization of stats:
1) Cooldown reduction on paragon, shoulders, offhand, and gloves are mandatory. You might also consider CDR on rings; don't get it on amulet.
2) Attack speed is almost totally useless for this spell, Explosive Blast does not benefit from it. Do not sacrifice any stat for it.
3) While the best stats on amulet/rings are CHD, fire damage, intelligence, and CHC (in this order), you should also look out for jewelry pieces with at least two of these stats and a socket - for legendary gems in 2.1.
4) Do avoid high life, focus on mitigation. 300-400k life is perfectly fine; get high armor rolls (550+) on Tal's chest and Captain's legs.
5) A perfect Tal's chest would come with a high armor roll (550+) or elite damage reduction; in that case you can roll off the attack speed to the respective other stat and have a maximum mitigation Tal's chest, or re-roll the attack speed to Explosive Blast damage (don't do this if it's your only Tal's chest).
6) Try to get Explosive Blast damage on chest, shoulders, and source.
7) For a detailed stats breakdown per slot, check thischeat sheet.
For amulet, Tal's is just the best, but any other will do - as long as it has decent stats. For belt, String of Ears is the defensive option, Witching Hour the offensive option, and Tal's just to complete the set bonus.