As was mentioned, hash tables are a good way to handle this, however, if you want to use variables, then you need to work with dynamic variables.

A lot more information (such as how the person is notified if they win, how they go about lowering an opponents hp, how you're going to determine a person's IP, what happens if the number of hp gets to a certain level, if the information needs to be stored even if the bot is offline, and probably others) would be needed before any kind of code could be decently written