[SoekiWiz]

Mind you only humanoid mobs will equip gear you give them.

Assuming you already know that, optimal pet gear would look like this:
2x Adamantite Bands (-20MR)
Rusty Spiked Shoulderpads (-10MR)
Riptide Spear (-5MR)
Tome of the Eternal (-10MR)
Astral Legs/Cloak of the Titans (-10MR)
Tolapumj's Robe (+36% Haste)

Other notable pet weapons:
Velium Swiftblade (If you don't need a proc weapon) - 36% haste
Ghoulbane - Up to 132 Undead DD procs @ L20
Staff of Undead Legions - Up to 585 Undead DD procs @ L46
Dawnfire - Up to 585 Undead DD procs @ L40
Gold Plated Koshigatana - Up to 162 Summoned DD procs @ L30
Steel Hilted Flint Dagger - Up to 625 Fire DD procs @ L50
Axe of the Slayers - Up to 90pt dmg absorb + str procs @ L30

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These are all bells and whistles, the main thing is just getting the pet to double attack. That will increase DPS significantly. All you need to do for this is hand it something that is "secondary only" to make it dual wield and activate the off-hand swings.

Torches, Lanterns, Shields, Instruments, whatever tickles your fancy.

Have fun~