Both you and your friends can get rewards via the Friends & Benefits feature for just playing Gangstar Vegas.

Go to Profile > Benefits. Here, you can do following:
- Enter your friend's Code to instantly get a pack of rewards
- Share your own Code. You have only 1 Code to share, but can do so multiple times. When other Gangstar Vegas users activate your Code, you progress through 5 milestones, unlocking more and more rewards.

Once all rewards are received, you won't be able to access the menu again unless new milestones appear.