u all suck.
The best way is always opinionated, but overall the best ways to get the most money the fastest is either Digging or Car missions. Digging gives you less money in time, but I've known people to actually get more money digging, again, opinionated.
I like Car missions because you can get 35-75 Graalats PER mission, and I can do a mission in under 30 seconds on IOS (yes it does make a difference), the mission lady near the VIP shop on the map is the easiest to use, just go up to her and walk into her over and over and grab and spam until it says "Read your P.M!" I've made $20,000 Graalats one day doing this starting from scratch