Accountant (coin icon): increases the number of coins your friend earns by 10%.
Keeper (blue star icon): increases the amount of experience your friend earns by 10%.
Strategist (energy icon): reduces your friend's energy consumption by 10%.
Ranger (red star icon): increases your friend's chance of finding collection items by 5%.
You can also charge your friend's trophies to help them get more bonuses from them. When you leave help at merchants', you reduce the time it will take to fulfill your friend's next order by 25%, regardless of your talent.
Help your friends out like this, and they'll return the favor.
As a reward for your help, you'll get coins and experience. You also get reputation points by helping your friends. The higher your reputation, the more free gifts you can send your friends.