Why focus so much on individuals? Look at the countries where gambling is 100% legalized, such as Macau and Monaco. These countries have become super-rich due to the tax revenues from casinos. Also, huge number of jobs are created as a result of gambling.
Bad effects will occur and the impact will be greater than the good one. Not all countries can legalize gambling even though the potential state revenue that can be obtained from this sector is quite tempting.
You have discussed both the good and bad aspects of gambling. It is right that gambling can give you a big money in a short time, but it is also a fact that gambling can make a big lost for you in no time. I think that if we compare the profit and lost in gambling we come to the conclusion that lost in gambling is more that its profit.