Going through what mods and why:
[Steel Charge]: Melee is meta right now, (Though soon that will hopefully change) and [Steel Charge] gives more added aura mod capacity, allowing for one less forma.
[Speed Drift]: Extra sprint speed fits [Gauss] and it's just more fun. Casting speed helps offset Redline's long animation.
[Primed Continuity]: [Gauss] really needs duration for Redline and kinetic plating to do anything.
[Narrow Minded]: More duration.
[Primed Flow]: The extra energy helps [Gauss]'s main survivability in this build, and is just helpful in general.
[Rolling Guard]: Invincibility and cleansing status effect. Invincibility is useful... obviously, but it also helps if you need a get out of jail free card in a bad spot.
[Adaptation]: [Adaptation] is a really helpful mod, especially in this build, as it helps [Quick Thinking] and [Gladiator Finesse].
[Quick Thinking] + [Gladiator Finesse]: These two mods, when combined with everything else, Kinetic Plating, [Primed Flow], [Adaptation], Arcane [Guardian], essentially make [Gauss] unkillable. It leaves [Gauss] on 2 health, but with Kinetic Plating active, you gain energy back while getting hit, letting you use [Quick Thinking] + [Gladiator Finesse] more.
[Pyroclastic Flow]: Let me have my fun.
Arcane [Guardian]: Extra armor to help [Quick Thinking] + [Gladiator Finesse].
Arcane Nullifier: If you get any kind of magnetic proc, you will just die instantly, so this is important.

The combination of [Quick Thinking], [Adaptation], [Rolling Guard], Arcane [Guardian], and of course, Kinetic Plating, gives [Gauss] an effective taking method that doesn't need a lot of micromanagement to work. Because you'll be moving around more, and hit less by enemies, it's still effective at high levels, including Steel Path.