Before installing Gallery on your own server, you might first want to see it in action.
You can freely configure this demo installation as 'administrator and see how your changes affect the look & feel as well as the functionality of Gallery.
Note that the demo server of opensourcecms.org does not offer all features though. Some optional features need external tools that are not installed on their test-server.
A quick way to play with all features of Gallery 2 on your own computer without worrying about dependencies, webservers and such things is the Gallery Virtual Appliance.
Basically you download a single file, run it and voilà, you have a running Gallery 2 server on your computer (which can be quickly uninstalled as well). More information can be found at: Gallery Virtual Appliance.
Gallery is free and open-source. It doesn't take a lot of time to install it yourself. Why not give it a try?