Master Missions this week

http://fate-go.cirnopedia.org/master_mission_us.php#nav

Undead skeleton is everywhere in Fuyuki, Assassin gem is pretty easy to get on Oceanos ( ghost enemy from the ship, i forgot the node ).
You can hunt it too on Camelot free quest, but the ghost is harder to beat.
Camelot also have so much berserker in the node, the easier ones is on Septem.
Undead is something like Ghost, Zombies, Skeleton, or etc.
Dragon is something like Artorias, Kiyohimes, Liz, Shuten, Wyverns, Elder Dragons or etc ( maybe you can instantly kill a Dragon by turning any enemies/servants into Dragons using Georgios, but the system will not tell you kill a dragon anyways ). Georgios is present or still alive then anything is a Dragon.
Wild Beast is a typical beastman like werewolf or etc.

Golem/berserker - Septem
Wyvern/rider - France
Skeleton/knights - Fuyuki
Pirates/knights, Cavalries - Oceanos
Werewolf/knights, Cavalries - Septem
Dragons, there's Kiyohime on the Rerun lite 40AP Node
Shadow servants/Knights, Cavalries Camelot Shadow Gawain/Oceanos Shadow Heracles.

My listed master mission here is used personally by me, as i find the material outside training ground is pretty good here.
That's my favorite place for finishing ''ordinary'' master missions.
Though it's up to you, my listed place maybe not the best for most peoples but for me i found it truly easy to clear most master missions using that place/singularity.