Theres an option when your gifting bushes, you can with out using diamonds and coins, give your friends..

When a player receives a bush as a gift, the player can either keep the bush or sell it. If the player sells it, they receive one of the items that the bush yields.

"Yields" means what your bush recipient may receive when they dig up your bush. It is not something for you (the giver) or something you can use to purchase a bush. For example, the Marmalade bush (orange bush) can give your recipient either a building material (toolbox icon), gold bars, or diamonds. Likewise, when you receive a Marmalade bush, then you may excavate it, and you will receive one of the yields: building material, gold bars, or diamonds.