I have an i90 BRD, and have cleared T5 multiple times with many different sets. Until you start getting T5 clears and have more loot to work with, aim for this set: http://ffxiv.ariyala.com/LNJR

That means clear all EX Primals and get your Elfin Bow, then farm Ultima until you get neck and ring.
Myth priority should be belt>gloves>earrings>wrist.

That set will have you at the cap to hit Asclepius 100% of the time after eating HQ Deviled Eggs (don't bother eating outside of Coil if you wanna save some dough), and an absolutely massive amount of crit and det.

Both Crit and Det for BRD is somewhere around .3:1 ratio to Dex.

Good luck.