My personal build for general use and Steel Path.
Works great both solo and in teams.
Generally I wouldn't recommend running strength in the build, 100% is fine.

-Grenade Fan :

Shield Gating is an effect that occurs when shields are fully depleted, which prevents any excess damage leaking into the health pool. Warframes, Companions, and Necramechs gain 1.3 seconds of invulnerability upon hitting the shield gate, only resetting when shields are allowed to fully replenish. If the shield is still in the process of recharging after the gate has activated, the shield gate will only last for 0.33 seconds.

-from https://warframe.fandom.com/wiki/Shield

• [Protea] has 450 shields at level 30. A shield grenade (Holding [Protea]'s 1) will refill 500 shields which means that it will provide the full shield gating effect the next time the shields gating is triggered. Not only that, but [Protea]'s Shield grenade will also increase the invulnerability by extra 2 seconds, so you have now 3.3 second shield gating instead of the usual 1,3.

• When you use the ability once , it will scatter 4 grenades , which means with a single use of Grenade Fan , u can stay immortal for 1,3 seconds when shield gating occurs first time , then another 13.2 seconds using the grenades assuming u are getting rained down in bullets from enemies .
  It is also possible to use the ability several times in both modes since there is no limit to how many grenades u can have on the ground (Which is kinda broken).

• The slash grenades can provide a nice amount of damage on low levels and an unhealthy amount of cc on steel path (Every time the grenades do a tick of damage , they will stagger the enemies and have a chance of providing a slash proc)
  This means u can basically secure a small area by throwing slash grenades in several directions and it will keep enemies from shooting at you and slow them down significantly.

-Blaze Artillery

This will be where the most damage will come out from your build.

• There is a maximum of 3 turrets at a time (deploying a 4th turret will remove the first and so on).

• Turrets fire infinite punchthrough (but not through walls , it cannot aim them anyway) bullets which have guaranteed yellow crit and Heat proc.

• When you deploy the turret , you can see a circle on top of it that has a counter. That counter will increase every time it hits an enemy and will multiply the base damage by that number. This is also true for multi hits , which mean that if a shot will hit 4 enemies at same time , it will increase the combo counter by 4.

• The counter can increase infinitely but is limited by its low active time . This is why I recommend focusing on duration instead of strength .
  My current build features 207% duration which gives turrets a lifespan of roughly 6 seconds.

• You don't have to max the range since it will give you negative strength . Instead , just use every other mod except Overextended which will provide enough range for both normal missions and open world (around 57m).

• In normal missions it will mostly 1shot enemies so just spawn 1 at different angles to cover most of the map.
  -In Deimos , some enemies have some kind of extra damage reduction against NON-CRIT hits. Since the turrets shoot guaranteed crits , this will bypass this type of restriction and deal the full damage.

-In Steel Path , it is recommended to use an ability to group enemies so that you can increase the combo counter faster.
I would recommend using subsuming [Nidus]' Larva since it will provide the best position for enemies to get hit multiple times and reach 50+ combo counter (which will either 1-2 shot enemies or accumulate a huge heat proc and get burned to death the next second).
It is also worth mentioning that heat procs will lower armor by 50% which is quite profitable in killing grineer.

-Dispensary

Protea's play-style is focused in spamming abilities. Since all abilities require energy, a soruce of getting that energy is needed , and honestly it can be easy with just normal dispensary in normal missions since it doesn't have that much spamming but in Steel Path it is not enough. That is where my build comes in place.

• Dispensary will spawn 3 pickups : an EMPOWERED health orb(100 hp) , small energy orb (25 energy) and universal ammo(10% max ammo) which 3 sec delay in this order respectively .
  There will only be 1 pickup of each spawned at a time( so to spawn another health orb you need to pick the hp orb that spawned from the dispensary first). However there is a chance of spawning 2 of the same pickup which is affected by strength (Base 25% ). So be sure to use it every time when u get the +100% strength from Protea's passive.

• It is not possible normally to collect a health orb when hp is full (Same thing for energy and energy orbs).
  However , there exist 2 mods that let you collect health orbs: Energy Conversion for warframes and Synth Fiber for companions .
  -[Equilibrium] is another mod that can will provide extra energy based on a percentage of a health mod you collected (Maxed mod provides 110% conversion).

• Using both [Equilibrium] and one of the other 2 above will make you collect an EMPOWERED health orb( from dispensary ) and give you 100 health and 110 ENERGY. Assuming you used the passive strength bonus , you can possibly get as much as 220 energy from health orbs and 50 energy from energy orbs while you wait for the next rotation of pickups.

• I strongly suggest that you use [Synth Fiber] since it saves you slots for survival or more optimization on your warframe's build.
  Also I recommend using it on a vulpaphyla since they can revive even when they are killed (but keep in mind that you are unable to activate [Synth Fiber] while vulpa is in larvae form!).

Temporal Anchor is useless here

You can still use this for some random fun on low level. On high level using this has alot of risks.

So please change this to something more useful if you are doing steel path.

• Use either an ability that group enemies(i.e. Nudus' Larva , Zephyr's Airburst, Khora's Ensnare etc ).

• Personally using [Nidus]' Larva since it synergies pretty well with Turrets, making them stack combo faster and higher .(There is also a certain bug with ragdolling effect which makes enemies get hit several times from same shot , forgot if its still possible with turrets but it works with Mausolon at the moment)

• Another option would be using your 4 for another type of utility and using [Proboscis Cernos] for grouping enemies. For this playstyle, i prefer using [Sevagoth]'s Gloom for some slow or [Wisp]'s Breach Surge for more damage.

MOD Changes

Aura : I usually go with [Enemy Radar] since It is quite good for seeing where enemies are spawning in steel path even when the pet is down. Other options i would say [Corrosive Projection] or [Growing Power]

If you are having problems with getting grappled or koncked down , change [Cunning Drift] with [Primed Sure Footed] , if you don't have it , you can use [Handspring] instead.

Since shield grenades give overshields , you can change [Constitution] with [Adaptation] ( [Adaptation] gives damage reduction to shields) .

[Rolling Guard] can be changed to [Vitality] on lower levels , but on Steel Path I strictly suggest you stick with [Rolling Guard] ( it is good for negating magnetic ,toxin and cold procs, others won't affect much ).

PLEASE , DO NOT MOD FOR SHIELDS!,
If you go above of what the shield grenades can 100% refill on initial cast , then you won't get the 2 seconds shield gating invulnerability.

Arcanes:

Not necessary unless you want to min max to full potential.
Arcane Energize is useful whenever you are extremely low on energy (which shouldn't happen often ) or at the start of the game to get enough for using dispensary.

Arcane Aegis is nice since it will provide a good amount of shield gating time to further help surviving .

Arcane Eruption is underrated. Since you will get health orbs all the time , it will provide a good crowd control to enemies near you.

Arcane Resistance and Nullifier can be used depending of what faction you are fighting against (ex. nullifier for . They won't matter much unless you are on Steel Path .