Mr. Hoffman has always been cautious with his money, but over the past two weeks he has developed grandiose plans to bet his entire life savings on a single horse race. With unrestrained exuberance he has also been giving everybody he sees unsolicited advice on how to make millions in the stock market. Mr. Hoffman's behavior is most indicative of:

mania

Explanation:

Based on the scenario being described within the question it can be said that Mr. Hoffman's behavior is most indicative of mania. This is a phase of bipolar disorder in which the individual begins to experience intense energy, rapid thoughts and other exaggerated behaviors that are not normal for the individual. Such as suddenly wanting to bet all your savings on a horse race, as is the case with Mr. Hoffman. Which is a behavior that is completely abnormal for him.