If you enjoy clicking to get the regular prize and finding the bonus prize, good for you.
However, if you're lazy like me and wish to get it done easily,
you can get Bat's Advent Calendar Auto-Collector(you need an account to see links)
OR you can get j03's StealthCORE dailies bot which will also collect both prizes and more (you need an account to see links)
*Only clraik rank and above and/or (you need an account to see links) can use this script/program!