After Chapter 2, you will start farming more money from the story missions. During Chapter 3, you will start getting optional missions from the gang members. You can skip these if you want but on attempting these, you will farm some cash out of these. The side missions usually contain rob...
Do some story missions, then do some side quests, spend a bit of time at camp, go hunting and fishing, go exploring, do some of the challenges, just ride around and experience those random encounters as they occur. If you are on the PC, consider using a trainer so you can head into...