For me I told him that he should know that gambling it's a game of risk and luck, but with the constant betting you might win the amount you've at mind someday. So what are your suggestions towards this.
Sorry to say that you are just misleading your friend in this situation and will probably make him to lose more. On a norms, gambling is supposed to be an avenue for entertainment and fun but we have changed the narrative long ago, we now see it as avenue to make money forgetting its traditional role. In a situation like this of your friend, you should have just tell him the plain truth regardless of whether he may listen or not. Let him understand what gambling is all about and there's no guarantee of making profits in return. If he's so concerned about making profits then he should take a break if the profit is not satisfactory. Telling him to keep gambling constantly and might probably win big someday is the worst advice I have come across in gambling industry.
Unfortunately, many people start their gambler's journey with an insanely huge bet. For example, when my friend received an annual bonus, he went into a room with slot machines and lost all the money.
And when he came to himself, he went to borrow from all his friends, because his only goal was to win back this money. And of course he lost everything that was lent to him. This is the price of ill-considered money management.
This is one secret about gambling but many people/gamblers are yet to figure it out especially those who are new to gambling industry. When you play game and lose, the best thing to do at that moment is to stay away from gambling and come back some other time with different mindset but if you stay back with the intention of playing more games just to recover your lost money, you will definitely lose more money. It's a proven fact that we have been seeing it happening regularly. The case of people succeeding in such scenario is very few.