I’d recommend to spec something like this: http://thepresequel.com/Jack/00000000000000550505003001500515003000
The key skill in this build is Leadership, which procs all your kill skills (Synergy, Winning, Believe and Absolute Advantage) when your Digi-Jacks die, which can be achieved very easily by simply walking away from them. Absolute Advantage is the big one here, because it allows you to shoot for a very long time without reloading, and you can keep it active as long as you keep moving. Teamwork and Winning will keep you alive as long as your Jacks die.
I’d try to find a class mod that boosts Absolute Advantage in order to improve your chances of not consuming ammo. This works very well in combination with Jakobs shotguns such as the Flayer, Quad, Coach Gun etc. Hyperion shotguns like the Development and Thinking and Splitters of any manufacture also work quite well with it.