It's still gambling because you're spending money to earn money and competing with other people for the prize money.
But if it's a game like GTA, Mobile Legend or any other game, you can make money from it because I see many people offering to sell their accounts to other people.
From there, they can get their money and if you are an expert in the game, you can generate many accounts to sell in the free market.
But I don't know if there is an online casino site like you mean.