You can only re-gift giftable items. When you choose to re-gift an item, its posted to your feed so any of your neighbors can claim it. When you re-gift an item, you can select how many of that item you have in your gift box to re-gift, from 1 to the max number you have. You can do a re-gift feed up to 4 times per day, regardless of how many items you share each time you re-gift.