Gambling is paying money for a chance to receive a prize of greater monetary value. It’s not just taking a risk. It’s creating an unreasonable risk.
Free door prizes are not a form of gambling because no money is risked in receiving them. Investing in stocks is not gambling because it is helping someone run a business it involves partial ownership and it demonstrates wisdom in planning for the future. And insurance is not gambling either because it is also a preparation for the future.