Concerto Competition?

[EuphoniousJoy]

So Colorado State University holds a concerto competition every year. I have never done it, but I have been thinking about doing the competition this year.
I play the Euphonium.

What type of music should I look at for this type of competition? I have never done anything like this before, so I'm not sure what type of music to look for either. Please help!
thanks!