Ok, first off this is RISKY. I have made about 5 mil profit on Asura starting with 100k but some days I have lost over a mil, but some days I make 3 mil profit alone. Gambling in game is 100% legal (in game) now as long as you don't scam. I will first explain how to casino for anyone who doesn't know about it.
Gambling is using the /random feature to get a number 0-999 and accepting other peoples bets.
Requirements: At least 10k to start but i recommend 100k to make good gil.
The first step is to get good odds. I use the odds that 200-400 = x2 gil and 700-800 = x3 gil. (If you are good at math this gives them a 30% total chance of winning, and a 70% chance of you winning.) You can customize the numbers, but I wide spread them like this so they odds appear better than they are. Also, the 10% chance of x3 can bring some people.
Next, go on top of the Jeuno auction house and type in your "casino ad" message (I recommend macroing it but don't spam the message to much or the GM's will get ticked.)
Mine is something like "Great casino above auction house! Accepting 100k-1mil bets. 200-400 = x2 and 700-800 = x3." (if you are a noob adjust the bet to like 1-5k or something as long as you could afford a x3 win if they did obtain one).
People will then run up to you on the auction house and trade you their bet. For my example I will use 5k as my example. So they trade me 5k and I say like good luck thanks for playing (usually macro this).
They type /random. They roll 555 it says. I say "sorry you did not win, try again later

" (usually macro this). Lets say they try again with another 5k bet. They trade me 5k and type /random. They roll 340 (a winning x2). I say "Congrats you won x2 gil! Trade me for your winnings" (usually macro this). They trade me and I give them 10k reward (5k bet x2 = 10k winnings). If you are bad at math use a calculator so they don't get mad if you miscalculate.
People usually get addicted or stop once they are under in winnings, thus giving you profit. Occasionally you get a person who wins a lot in a row. If this happens keep your cool and hope they lose or cut them off and say I gtg.
Once you make enough gil you can stop and spend or raise your casino's betting amount to enable more profit. Then enjoy your winnings once you have enough.
WARNINGS:
1. Always make sure they pay 1st.
2. Make sure the roll is a /random and they did not type it as an emote.
3. Make sure you can afford the highest winning in case some1 makes that much.
4. Always make sure you know the amount and player name of the person who bet. You don't want to give them the wrong amount or give it to the wrong person or you are liable for paying them.
*Please use this at your own risk because I am not responsible for poor gambling techniques or other players luck.
Post any questions or comments below. I hope this guide helps.