How long do i have to wait before i can send gifts to the same friend?

You can send 1 gift from the Free Gifts page every 24 hours to each neighbor. However, you can gift as many items as you wish from your own Inventory to the same person. To do this, go into your Inventory, select the giftbox under the item you wish to send and then choose the neighbor and quantity you want to send. Using this feature does remove the item(s) from your inventory.