Essential Mods: [Brief Respite], [Rolling Guard] and [Blind Rage] if you're not using Hildryn's Pillage.

With modding as Nezha your priority goes Strength>Duration>Range>Efficiency

• Strength is key on [Nezha] as it increases your damage and damage amp on your 1 and 2, increases the rad status chance on 1, and increases your armor/absorption multiplier on 3 so you can cast it less.
• Duration is good for uptime for your 1,2 and 4. Mostly quality of life but still nice to have.
• Range only helps your 1 and 4. It's nice to have but not necessary at all.
• Efficiency you genuinely want to be negative so you can shield gate easier.
• Brief Respite, Rolling Guard and Blind Rage are essential for shield gating, if you get Pillage all you need is Rolling Guard and you can switch the others.
• Flow, Equilibrium and Arcane Energize are all for the sake of the Infinite Energy [Nezha]. [Nezha]'s 2 has a 100% chance to drop a Health orb. Along with Synth Fiber which allows you to get 27 Energy per kill, if you hit 2 people with your Chakram (and honestly you shouldn't just use your Chakram on one person anyways) you'll get energy, and if you hit more than 2 then you'll be able to get more energy to constantly cast all your abilities with little concern of the energy costs.
• If you don't have energy problems because of a maxed arcane energize, using zenurik, or simply because you don't care about the energy costs, replace Equilibrium with Transient Fortitude or Streamline and Reaping Chakram with Safeguard.
• Unless you're grinding out a mission where you need all the speed you can get, like Orokin Vaults or Void fissures, you want to Helminth your 1 as the speed increase in other missions, especially survivals or higher levels is pretty useless. Replace with Breach Surge if you're going against infested/low level missions and Pillage if you're going against Grineer/Corpus
• Arcane Energize is required for almost all frames that use energy, so use it. Molt Augmented is nice because it increases damage vulnerability from your 2 and spark damage from your 1. Meaning more damage. Along with decreasing the amount of energy you use to recast your 3.