Dice Duel requires both of the hosts to have the dice in their inventory. The rules of this game are actually quite simple, both of the hosts roll their dice once and the player that has the highest number gains a single point to their score. The first person to reach the score of 3 first is the winner of the game.
The first thing that you would want to do starting this game would be to find a trusted host who offers the Dice Duel game. There are clans that you can join and other people you can gamble with.
Before you agree to everything and rush into starting the bet, be sure of two things: 1, you're both in the same clan chat and 2, you have both confirmed that you're playing the same game. There's been a lot of confusion in the past and reports that players haven't confirmed what game they're playing with each other. For example, the host may think you're playing Blackjack whereas you may think Dice Duel.
The next thing you would want to do is trade the host the amount of money or item(s) you would want to bet. As stated above, the aim of the game is to get a higher number than the other person 3 times. The first person to reach 3 points is the winner of the game and the money/item(s) will be theirs to keep.