The usual charms that everyone uses are Power, Enduring, Infused. Power increases Crit damage, Enduring increases Endurance which reduces your damage taken, and Infused increases mana regen rate. Zerkers are always mana-starved so Infused is the most important charm you can use.
As a zerker you'll be wanting anything that increases your Crit, whether it be Crit stats on items, crystals, consumables, or a pocket mystic who can follow you around and give you that DFC (Delicious Fat Crit) aura. A zerker without crits has embarrassingly bad DPS, we depend entirely on landing crits for our entire DPS output. For most of your leveling career you'll want to tote around Scrolls of Carving until you're level-capped and you have a bunch of Crit bonuses on your gear, then you can switch to Scrolls of Savagery for the Crit damage boost. Your only 100% essential crystal that should always be on your weapon is a Carving crystal, the other crystals will vary based on what you're doing.
