Currently the duel system is basic to say the least. Our only command is

/duel <amount>

You can't set up a first to 3 duel with commands and you can't use items either so I think this needs a change.

/duel <amount> <amount of matches>

This would be the best of x games duel command. For example /duel 10000 5 means that whoever wins more out of five games gets the duel amount.

/duel <item>

Not sure if this command is possible but yeah this is basically an item duel command. The way it works is simple. Type in the command and you basically bet your specified item on yourself. The item will go to the winner in the end. Now this is not a failproof command as you can see. How do you make sure that you get something aside from your item if you win? Our next command is there to solve that problem.

/selfbet <amount>

You bet an amount on yourself that goes to your opponent if you lose. This can counter the duel item problem.

/duel <item> <amount>

This is the same command as the other two just combined. You place your item and set the amount of TC your opponent loses if you win.

/send <amount> <player>

This is not really a duel command. Just a way to send TC in-game. A fast and convenient method.