Fervent Monstrologist here. I don't know how to answer this
Monstrology being my favorite Wizard101 hobby, I have a collection of literally hundreds of unique house guests. My targets are often House Guests that are unique in either sprite or animation. My decisions are based on personal preference of the animation or sprite. I'm not saying this to brag, but I'm trying to say that my decisions are influenced my my own choices. If you were to look at sprites and animations, I am sure that you would make different personal preferences than me.
If you're adding Monsters to your Tome, I would suggest looking at fansite Final Bastion's Monstrology section. It contains a complete list of what monsters can be found in which world. It has an image of what the monster looks like, so you can make your choices about what to hunt first.