With tricks and cheats, you can win without any loss. However, it is still a game and not real. These casinos are risky in the same way that real-life casinos are. On your third visit, you will see that the place is now filled with monsters and the upper Octagonia is now a casino. You will be able to find the Octagonia casino on your third visit to it. The other Dragon Quest 11 Casino is located in the North of the Dundrasil region in a town called Octagonia. Using that slot machine, you can send slimes on a quest to win you tokens.
In that casino, you will find a slot machine surrounded by people. It will be accessible to you as soon as you get the ability to sail. You will find the first casino in the town of Puerto Valor adjacent to a hotel, and the line of people waiting outside quickly draws your attention to the entrance. If you are a beginner who has just started playing dragon quest 11, it might be hard for you to locate the casinos.