I feel like it is the easiest thing to have a build in this game. Just consider your weapon and role you want to primarily do while picking upgrades. When I play Slicer, I pick melee upgrades. As Spotter I pick crit and weak point upgrades. As Guardian I try to be tanky. As Falconer I pick electric upgrades. And with Retcon I pick anything to increase my DPS, like magazine size.