Galavax benefits from:
Additional Low-to-no Flux DPS (Cha'Kru Chas'ki, Endari Needler)
Mobile Healing (Cha'Kru Cultists, Tow Bots ; Gensis Core)
Reliable Tanking for Non-Sacrifice-focused Builds (Valkaru Hounds)
Support Spellcasters (Arandi Ethermancer, Arandi Chronowarper)
To complement Galavax's functionality, I recommend your equipped items to be:
Enigmatic Capacitor (5% Faster Ability Cooldowns per Level)
This upgrade can make Galavax's Lighting Blast have a 0sec Cooldown after killing an enemy
Utility is pretty much limited to Galavax Himself however ; Other units rely on Energy, not Cooldowns
Gensis Core (+1hp/s Regeneration outside of Combat per level)
This item has low utility until level 4 sadly
However it is a great boon for Galavax's general lack of healing and low hp units
Not worth the cost to upgrade to level 5
Arandi Penumbra (Grants Access to the Arandi Mercs in Missions)
Most Expensive Mercenary Faction
Also the only one that actually synergizes with Galavax's mechanics
Keep 1-3 Arandi Ethermancers in your army; they will ensure every Thrall and Steelsworn death counts twice
That includes buffs from sacrificing units; You can sacrifice the same Steelsworn twice and fully restore a Terror Tank
Arandi Chronowarpers can provide good utility due to their Time Slow ability
Other Arandi Units are not an efficient use of resources for Galavax
Phoenix Guards are simply not worth the Flux; Asterions are fragile and out-dps'd by Galavax's Regular Roster
Galavax also has limited synergy with the Corsair Merc Faction, as Raiders can steal Flux from enemy Harvesters
Enemy Flux Harvesters are not guaranteed to spawn however, and otherwise the faction does not provide much value
Galavax also has limited synergy with the Cha'Kru Anqas & Valkaru Merc Factions, as they can provide healing and extra DPS
Without an unit retention buff, Galavax gains the least power out of these added units
The Cha'Kru DPS unit does not cost Flux and has better DPS, giving it more utility
The Valkaru units are tankier and match the speed of Galavax's regular roster, on top of providing more AoE support
However, the utility of sacrifices counting twice cannot be understated