Not even savescumming. I'm not sure if I got really lucky but I feel like spamming the most expensive option in the casino will always be a net positive after some tim.
You do normally walk away with more than you spend, but you can hit an annoying losing streak that slows you down. Save scumming just lets you get to 1 mil a bit quicker.
Quickest way I got was spamming the Galactic Union Missions. You send your crew out on them, and I racked up money pretty fast. That and working at the club
