Summary

This build is all about taking zero damage as Gauss. His 2 gives up to 100% damage reduction (in relation to battery percentage) against IPS (Impact/Puncture/Slash), Heat, Cold, and Blast. This works great against Grineer, but leaves you a bit vulnerable to Corpus and Infested. Their IPS damage will be blocked, but their Electric/Magnetic/Toxin/Gas damage will not. This is where [Vitality], [Quick Thinking], and [Gladiator Finesse] come in. More on that below.

How

Keep Redline (4) and Kinetic Plating (2) up at all times. Spam Mach Rush (1) to keep your battery topped up until Redline stays at 100%.
After about 1/2 of the duration of Redline has passed (can't find exact amount anywhere), it will stay at 100% for the remainder of the duration. Once it ends, you'll be at 80% damage reduction until you recast and fill it back up.

Mod Choice

Aura

Depends on the activity as always, but unless another aura is called for, [Energy Siphon] has great synergy with Kinetic Plating's energy return, [Quick Thinking], and [Gladiator Finesse].

[Power Drift]

Enough strength for your 2 to hit 100% damage reduction

[Primed Continuity], [Narrow Minded], [Constitution], and [Augur Message]
Max uptime on 2 and 4 and max buffs on 4

Vitality, Quick Thinking, and Gladiator Finesse

Buffer against any damage taken before Redline gets your battery to 100%/against any damage other than IPS, Heat, Cold, and Blast

Primed Flow

Quick Thinking/[Gladiator Finesse] buffer