An example for a wordpress site, but basically ignore everything and then add exceptions starting with ! for what to include
# Ignore everything in the root except the "wp-content" directory.
/*
!.gitignore
!wp-content/
!wp-config.php
#
# # Ignore everything in the "wp-content" directory, except the "plugins"
# # and "themes" directories.
wp-content/*
!wp-content/plugins/
!wp-content/themes/
#
# # Ignore everything in the "plugins" directory, except the plugins you
# # specify (see the commented-out examples for hints on how to do this.)
wp-content/plugins/*
# # !wp-content/plugins/my-single-file-plugin.php
# # !wp-content/plugins/my-directory-plugin/
#
# # Ignore everything in the "themes" directory, except the themes you
# # specify (see the commented-out example for a hint on how to do this.)
wp-content/themes/*
!wp-content/themes/twentyeleven/