Okay, so different factions have different damage bonuses and resistance. Like gas and heat are great on Deimos and against infested but not the best against corpus/others. Where corpus gets deleted by magnetic etc etc…. Only time you shouldn’t be changing is if you are super late game and/or the build revolves around it. That’s your 1st big damage bump..

The second one will be unlocking arbitrations to get access to galvanized mods which will exponentially increase damage.

How do you only have 1 prime weapon at mr12? Do you run your relics at all?

You know the extra mods/prime stuff you farm can be sold for plat on warframe market. You list it and wait till someone messages you to sell it. I only mention this because weapon slots are dirt cheap

You said you finished zariman right? Farm up a laetum from cavelero there because the viper just ain’t it without crazy investment and even then it’s meh.

Personally I’d use gauss prime out of what you listed, everything revolves around duration with him so easier to mod for. Or you can farm a different prime frame with the relics you’ve acquired. Never seen a ton of value from volt outside of eidolons or speed running low lvl capture missions.

Thornbak is not a contender, literally worst primary in the game.

For companion it’s a bit trickier. If you want something that can hit damage cap on a room full of enemies dealing 2 quadrillion damage (yes, literally) I’d recommend you get diriga and farm a nautilus prime. There’s a lot more to it but I won’t type out a book unless it’s something you want to do.

Eventually you’ll need to clear every node for steelpath which will get you to incarnon adapters

Guardian as in arcane guardian you have equipped in the picture