Raw damage critical setup for the purgator (using mods that I have ingame). It is not worth using Hunter's Munitions or any damage over time status as we want to get direct kills with this weapon to use its unique trait which creates a gas cloud on KILLS FROM DIRECT HITS.

Considering that this weapon already fires slow as it is, running [Semi-Rifle Cannonade] is not a bad choice and allows us flexibility in any arcane we can take, whether it be Primary Deadhead, Primary Crux for its ammo efficiency (which allows us to forgo [Ammo Drum] and slot in something else), or Primary Exhilarate (if you want to bring it for energy [Regen] purposes with damage on the side). Primary Merciless can work as the reload speed is a godsend for this gun, but for consistency Primary Deadhead is better. We can take Bane over [Ammo Drum] as [Vigilante Supplies] or [Sniper Ammo Mutation] (in my case as I don't have vigilante yet) should sustain this weapon enough with [Ammo Drum] being a quality of life due to its already low ammo pool. Unranked ammo mutation as you're only getting 1 round per ammo anyways (Note that this doesn't save a forma at all.).

[Magnetic Capacity] for magazine size.

In terms of Riven Rolls, its a 1 Disposition, it is best to get a roll that helps the weapon feel better such as reload speed, maximum ammo, projectile speed. Any offensive stats will be better if a negative is present but still not really worth bringing and honestly can be dropped until this weapon has a higher disposition as it is only really good if you can land precision easily.