I also had to go from 770k to 1mil, but I was able to do so in the span of about 30 minutes. Ingame after Galiano gave you the money he told you to "hit the casino" to get to 1mil. So I went to the casino and spammed the 1k option (I wish they would maybe add a 10k option to go a bit quicker). You can either save-load repeat until you get a good roll, or spam-click and hope for the best. I did both and the spam-clicking seemed to go quicker (you lose a lot, but hope to win a lot). Maybe I got lucky, but give it a try.