Build specifics

Aura and Exilus slot
I rarely find myself using Growing Power due to the condition it has. If you also don't feel like using it you can choose something for weapon damage or utility.
For the exilus, if you find the extra 15% ability strength to be unnecessary, you can use Mobilize for extra parkour velocity, if you are using your 3 to move around Rush is perfect.

~ Those two slots are really up to you. Growing Power and Power drift are the better options but you might want to use something else which is more than fine and it doesn't ruin the build at all.

Archon Shards
2x Emerald shards for extra corrosive stacks to armor strip
2x Tau amber shards (parkour velocity)
1x Tau amber shard for casting speed -> this helps you survive at very high levels
If you don't want to run that here are some options:
1x Tau crimson for ability strength.
1x Tau amber shards (parkour velocity)

Helminth
Nourish: This is the best option for base steel path, it gives viral damage to all your attacks and you have an energy multiplier (which does work on Energy Nexus).

~ The nerf on nourish doesn't impact the build that much. The important part is that we get viral and more energy.

~ Other options you can run are: Roar, Xata's Whisper or Mind Control (replace Mesmer Shield with Thrall Pact if you do so, first cast Mind control and then thrall the enemy).

Focus School
Zenurik: This will grant you infinity energy with wellspring so you can skip using Energy Nexus and replace it with a mod of your choosing.
~ I mainly used this to fill the energy bar by the time reave stopped so we can move around easy. I will recommend it for capture/other fast missions if you do not have parkour velocity archon shards.
Madurai: Use this for 40% ability strength on your warframe and more damage on your operator.
~ In my opinion the only option for endurance runs (such as void cascade).

~ If you want to use some other focus school feel free to do so but those two are the ones I found more useful.

Arcanes
Molt Augmented: Better for longer runs, for shorter ones replace it with Molt Vigor.
Molt Efficiency: More ability duration = less casting though you can replace it with anything you like.

Weapons

Primary
Any weapon you like will do, I prefer Torid.

• I mod corrosive(a riven for this is best)/blast and nourish for viral (2 green shards) The damage is insane, if you need my build let me know.
  I also use the [Scourge] for void cascade, makes it easier to land headshots with dual tox

Secondary
Dual Toxocyst: Easy level cap weapon. It gives you toxin on headshot for a few seconds so modding for electricity gives you corrosive and with nourish you get viral too. You fully armor strip with archon shards.
~If you are struggling with headshots, especially in when you are with a group, you can use the Scourge which has a headshot attractor.
Grimoire: Excellent choice, you can use this to buff yourself even more. I use Xata Invocation however any invocation mod on it is amazing. You want more duration ? Can do. More ability efficiency, also good on it.
Any primer: Apply viral, you can use your 3 to kill.

Melee
For damage you can run either the Cerata or the Glaive Prime depending on what you are facing.
If you don't use melee much, Praedos is a fine choice for the extra parkour/sprint speed.

~~ Any weapons you feel comfortable with will work i just prefer those.