After finishing a fight in Tournament Rivals, it makes you wait 5 minutes before you can start another fight. It goes by real time so you can manipulate this by changing the time on your computer. I'd imagine just about everyone would know how to do this, but here are step by step instructions just in case.

1. Alt-tab to your desktop
2. Right click your clock in the taskbar
3. Click "Adjust Date\Time"
4. Turn "Set time automatically" to Off
5. Click "Set the date and time manually"
6. Set the time to at least 5 minutes ahead and click change

Alternative method:
1. Alt-tab to your desktop
2. Click the Start button
3. Click Settings
4. Click Time & Language
5. Turn "Set time automatically" to Off
6. Click "Set the date and time manually"
7. Set the time to at least 5 minutes ahead and click change

Now you can go back into your game and start another fight immediately, then keep repeating these steps (just leave the settings window open so you only have to repeat steps 1, 6, and 7) after each fight as many times as you want. It's a great way to gain gold quickly. If your health gets low you'll want to wait a little bit in the game for your health to get back up, but you shouldn't have to do that every time if you just stick with fighting guys you can comfortably beat without losing a lot of health. Or if you have a decent number of students, then you don't have to worry about it at all.

After you're done, just go back to your clock settings and change "Set time automatically" back to On. Once you do that though, it'll make you wait for as much time as you skipped ahead. So say you did it enough times where your clock is ahead by an hour, it's going to make you wait about an hour before you can fight again, so you'll only want to do change your clock back when you're actually done doing fights for at least that amount of time, or you can just mess with your clock again, of course.