Do you have jack installed and running? On Gentoo jack isn't installed by default and I am not too familiar with Gentoo to get you to do it.

But going down the lane, by your question, I need to ask you the following:
Are you a beginner in the Linux Audio world?
If yes, and you are just starting with Linux audio, I could recommend that you search and try some distros that are maybe easier to handle at the beginning? Like Ubuntu Studio, or AVLinux?