This build focuses on [Gauss]' fourth ability, Redline, as well as the Helminth ability Energized Munitions to unload a LOT of hurt, while using [Gauss]' second ability, Kinetic Plating, to make him nearly invincible... until a Nullifier decides to make a surprise appearance.

WHAT IS ENERGIZED MUNITIONS?

Energized Munitions is a Metamorphosis Rank 5 Helminth subsumable ability. All it does is increase ammo efficiency by 75% for 5s, meaning that a gun only consumes 1 round for every 4 rounds fired. The efficiency is unaffected by any mods. What makes it so powerful on [Gauss] is because of his fourth ability, Redline, greatly reducing ammo economy due to the massively increased fire rate, making Energized Munitions a direct counter albeit in much shorter spurts. This build raises its active time to 15s with reduced activation cost. Ever seen a [Kuva Zarr] unload 20 cannonballs in five seconds?

THE BUILD

[Gauss] uses a unique resource called his Battery. We keep Mach [Rush] in this build as a way of increasing the battery quickly at low energy cost, plus bashing into walls is funny.

Strength must remain at or above 100% so that Kinetic Plating can remain at 100% kinetic damage reduction at a full battery. Kinetic Damage is Impact, Puncture, Slash, Heat, Cold, and Blast damage. Because Kinetic Plating renders [Gauss] invincible to the most common types of damage, he has one of the easiest times blazing through a swarm of enemies with ease. Further, Kinetic Plating prevents [Gauss] from being knocked down, allowing him to go ham with explosives.
Do be warned that he is still susceptible to Toxin damage, meaning that the Infested, especially Toxin Ancients and Venomous Eximus units, have the easiest time dealing with him.

Redline is what makes [Gauss] a murder machine. Setting his battery into overdrive, [Gauss] gains massive buffs to Fire Rate, Reload Speed, Holster Rate, and Melee Attack Speed. The battery can then be pushed past a thin red line on the gauge, and so long as it remains above said red line, a percent counter on the right side will begin to increase, raising faster the farther [Gauss]' battery level is above the red line. At 100% power, [Gauss]' battery remains at the very top and cannot decrease at all until Redline expires, which makes damage taken from Kinetic Plating no longer reduce his battery, and thus the damage reduction that Kinetic Plating gives will always be 100%.
Duration is so high because Redline uniquely draws its buffs from Duration rather than Strength.

HOW TO USE THE BUILD

Keep Kinetic Plating and Redline active at all times. Use Mach [Rush] to quickly raise [Gauss]' battery level or to traverse a distance quickly. Energized Munitions directly counters his decreased ammo economy through Redline's Fire Rate buff, and further lets him sling lead, explosives, energy, and anything else you're using to commit violence, even more before he has to perform a very speedy reload.

ALTERNATIVES

Exilus slot is pure flex. Use whatever you want in there, I used [Rush] simply because of speed to remain within [Gauss]' whole schtick.

Aura slot is also somewhat of a flex. [Enemy Radar] can go in place of [Sprint Boost], I kept it in there because speed.

[Primed Continuity] and Primed Flow can be substituted for their lesser variants or their Archon variants if you do not have the Primed versions.

NON-ALTERNATIVES

Adaptation is a no-go. You're already taking very little damage, and its only use would be to reduce any Toxin damage you could be receiving, which [Rolling Guard] already does.

[Primed Sure Footed] is redundant on [Gauss] because Kinetic Plating already provides knockdown immunity for a very long time (this build being 1m36s before a recast is needed).

ARCHON SHARDS

Having at least one or two Amber Archon Shards with Casting Speed will help to cast Redline faster. This is entirely optional because Redline now grants Casting Speed alongside its buffs, making an Amber Shard's only purpose being to speed up Redline.

The other Archon Shards are up to you.