I suggest that you start with the example below, use it for a few weeks,
and tune it to accommodate your habits.

The media containing your aide databases should be physically
unmounted between scans. Alternatively, see /usr/doc/aide-$VERSION/contrib
for some example scripts that will help you gpg sign your database, for
online storage.

=== /etc/aide.conf sample ===
database=file:/mnt/usb/aide.db
database_out=file:/mnt/usb/aide.db.new
gzip_dbout=yes

/etc/ld.so.cache p+ftype+l+u+g
/etc/ntp/drift   p+ftype+l+u+g

/boot		R
/etc		R
/bin		R
/lib		R
/usr/lib	R
/usr/libexec	R
/usr/lib64	R
/lib64		R
/usr/bin	R
/usr/local/bin	R
/sbin		R
/usr/sbin	R
/usr/local/sbin	R
=/var/log	R