What Kind of Grand Charms for a Conc Barb

[triple-c]

working on a conc barb, and the guide does not say what kind of GCs

Have maxed:

AX Mastery
Conc.
Bos
Shout (Almost Max)
Whats Next:
Iron Skin
Bash
Also what kind of grand charms do you wear with a Conc barb? they all seem like they would help I am thinking combat but am unsure

[sXp]

When i was having conc barb i was switching between different types of charms this is what i have learn :
1. Its good to have bo charms keep in stash use them at the beginning only than leave them back in stash.
2. DONT USE SKILL CHARMS !
3. The bast ones are with attack rating and min dmg i think they own