you can replace primary merciless with primary dexterity if you want to be more melee focused

if you dont want a riven i recommend the [Phantasma Prime] instead, but with a riven do [Phantasma].

if no riven put a [Primed Cleanse Grineer], corrupted or whatever your fighting

if you want more damage forma [Shotgun Barrage] or [Blaze] and rank up [Incendiary Coat] all the way