We have some of the most intelligent people in the world working on extracting as much wealth as possible from high volume trading. For someone to gain money in the market someone most lose. Imagine if we had these minds working on solving real world problems that would actually benefit society. Just like gambling, trading is zero sum.
It's important to completely understand that law, to start earning at trading. 95% of people are losing money in long-term.
But i don't think that trading is "just like gambling". Traders/investors are helping the market, by taking the risk of "losing". Also traders are some sort of arbiter/judge. They are making the hole world progress faster and more effectively, by choosing the "good" projects.