Hay Day diamond buying list

I used to do this too. You can visit anyone in hay day in general without adding them as friends. Now, how they visit you? Simple, visitors can come via newspaper ads you have put up, or via some friends you have. You can visit them the same way too!

There are plenty of benefits of having friends. Your friends can help you, and you are rewarded for helping them in return!

Being helped by your friends!

Friends can help the player fulfilling their boat orders, buying their items at their roadside shop, reviving their trees and bushes and also by (indirectly) give the player random mystery boxes when the player visits their farm. Friends can give the player items that the player is low or empty on. By adding friends, the player increase their roadside shop space and gain new spaces to sell goods from.

Helping your friends!

Likewise, the player can help both their friends and unknown players. Helping friends gives benefits for the player as well as for them. For example, by fulfilling boat orders the player gains money and experience, while the person they helped gets a step closer to stocking a boat full. Helping other players is the only way to acquire gift cards, which can then be used to buy packages using the catalogue.

Quotes from the "Friends" page on the Hay Day wiki.

You automatically have one friend when you start the game, an NPC named Greg. You can also add more friends through Facebook if your friends dont mind app request notifications!

NPC Greg:

^{Image from the "Greg" page on the wiki}