[Archon Stretch] gives easy extra energy
Molt Augmented for longer missions, use Molt Vigor if you don't want to build it up.
Arcane Guardian for passive armor, combined with Adaption = Tank
3 umbral mods -> 19.2% extra tau resistance.

Exilus:
Fused Reservoir for easy of mind. You can switch this to Power Drift for even more Strength (+15%).

Helminth:
Nourish -> Extra viral damage shared with allies. Extra 4.1x energy multiplier! Also great for CC.
Extra: Helminth Invigoration buff +200% Ability Strength for 7 days

Archon Shards:
This is up to you. I use 2 Tau Azure Shards (2x +225 armor) and 3 Tau Crimson Shards (3x +15% Ability Strength)

Focus School:
Zenurik - Use Hardened Wellspring (+20% ability strength)
Other option: Madurai - Use Sling Strength (+40% ability strength)

Extras

Kitgun:
Pax Bolt -> +30% ability strength

Specter:
Nidus Summon the specter at the beginning and it will continue to link you, giving you a 1.2875x multiplier to your strength. Have it hold position where you want the Motes as to ensure Parasitic Link stays active when needed. This is technically semi-passive. However, it's possible the link breaks from distance or time. But it is very forgiving and easy to tell if it's active. If it does break, try having it Follow, then Hold Position again. It will automatically link you again if it's internal timer to reconnect is ready. This is the most impactful aspect of raising your Ability Strength, applying a massive 150~200 strength bonus. You can obtain specter blueprints from rescue missions. Since the specter gets your buffs, as well as a Vapor specter having the same ability strength as a Cosmic specter, you can just farm Vapor specters for the x10 blueprint.

Mission specific buffs:
Arbitrations - +300% power strength
Void Fisure - Double power strength
Duviri :

• Brimon's Nerve Finishers grant +200% Ability Strength to your next Power Strike or Warframe Ability.
• Fortified Will: Every 50 Armor grants 15% Ability Strength and Power Strike damage (Capped at +500%)
  Railjack - +10% Archwing Intrinsic Buff

Max Strength

Base (Apply Conditionals) 416%
[Power Drift] +15%
Helminth buff +200%
Max Archon Shards +75%
Madurai +40%
Pax Bolt (Kitgun) +30%
Specter +200%
Mission specific buffs not included

Total: 976% Ability Strength