Hand communication particularly in instances of formal speaking places the emphasis on certain words, but on the downside, when overused it can become a distraction from the message.
There are many disadvantages of using hand gestures. Some of them (By my personal experience) are: If it is something private you're trying to convey, other people (those who you don't want to know...
There is one where you put the tips of your thumb and index and third digit together while rotating your forearm repeatedly back and forth. I think it means that you want to be their friend.