The best method of installing Gallery2 on Leopard is to do so from scratch, and start with a blank MySQL database. If you have previously installed Gallery2 under Mac OS 10.4, and it's not working for you under Leopard, you’ll need to back up your old installation's media first, so you can put them back in their proper places once your new installation is ready.
If you choose to download the "typical package," be aware that the only place you will be able to upload files is from a web browser, not from your server. However, if you download the "full package," the "upload files from server" option will be available. You can always disable those full-package plugins you don't wish to use, and have the ability to expand your site's offerings later on by enabling plugins of your choice.
For those running Gallery2 on OS X Server for Leopard, this next bit of information is likely not applicable. However, if you're running a server using plain-vanilla Leopard, you need to know that Leopard's PHP 5 is not as robust as OS X Server's, and does not have as many modules. Why is this important to know? Because Leopard's brand of PHP 5 does not support the GD Library, which is important for posting your photos. How do you fix that? Download an updated PHP 5 for Leopard HERE [1]. Instructions on how to install it are HERE [2].
After you've installed the upgraded Leopard's PHP 5, use MacPorts to download Ffmpeg and ImageMagick using "sudo port install ffmpeg" and "sudo port install imagemagick" (without the quotes). You can install these before you install Gallery2, or later after you've installed Gallery2. In either case, you will need to tell Gallery2 where these programs are located, which will be in /opt/local/bin after those progams are installed.
Let's assume you've downloaded the improved Leopard PHP 5, installed it, and have also installed Ffmpeg and ImageMagick using MacPorts. This will be a good time to create your new, empty MySQL database, give it a name and assign it a user and user permissions.
Now you are ready to download and install Gallery2 on Leopard.
Choose the package you wish to download, and download it. Double-click the image to extract the Gallery2 folder and its contents. Rename the extracted folder gallery2 (or whatever you wish to call it), and move it to the "/Library/WebServer/Documents" folder (without the quotes). We'll assume you named it gallery2. In your web browser, go to your gallery2 folder (example: http://abcde.com/gallery2/) and begin the install.
Follow the directions given by Gallery2, as you install the program. After you've installed Gallery2, log in as admin, and go to Site Admin's "plugins" selection. Under "Graphic Toolkits," you can enable Ffmpeg and ImageMagick by choosing the "configure" option . Just tell Gallery2 that these plugins are located in the /opt/local/bin folder. (Path to Ffmpgeg is "opt/local/bin/ffmpeg", and path to ImageMagick is "/opt/local/bin/"). Make sure you use Gallery2's "Test Settings" to be sure you've correctly specified the proper paths. Once sure, select "Save Settings." Now, go back to Site Admin's "Plugins" module and activate Ffmpeg and ImageMagick.
At this point, you may activate or deactivate whatever other plugins you wish.
Now begin building your galleries, using the files you had previously backed up, or build new galleries.
You can find instructions on installing Gallery2 on Mac OS X 10.4 Tiger here: