I've created a blog post of charts that depict all of the combinations for monsters recorded on this wiki. I have gone through (or will go through eventually) all of the comments on each monster, and provided you with an easy breeding section. Hope it helps and saves some time! If you see any that aren't here that you've used, please tell me in the comments below.
Note: Bug and Flower is a very popular combination because it has very short fail times. That combination, other than Air, can result in only Bug or Flower, both of which have a breeding time of only 4 hours.
Shadow Monster []
First Monster
Second Monster
Contributor
Flower
Mountain
TinyDragons98
Mountain
Flurry
SuperFilo
Vapor
Spark
Paula K5
Pollen
Mountain
A Wikia Contributor
Magma
Vapor
A Wikia Contributor
Burst
Inferno
A Wikia Contributor
Tree
Inferno
A Wikia Contributor
Earthquake
Silk
Debsanaries
Earthquake
Frost
AleksA
Earthquake
Pollen
A Wikia Contributor
Flower
Bug
MyStoGan
Seacliff
Mountain
A Wikia Contributor
Cinder
Silk
A Wikia Contributor
Note: Many Shadow Monsters that resulted from the Flower+Mountain combination involved a Mythic Flower parent.
Light Monster []
First Monster
Second Monster
Contributor
Flurry
Flamegust
A Wikia Contributor
Flower
Mountain
Spectreofflame
Tree
Flower
Paula K5
Frost
Inferno
A Wikia Contributor
Flower
Bug
Ash717
Earthquake
Tundra
A Wikia Contributor
Frostember
Flare
Xiaoxuan Dai
Sunstone Template:LightTemplate:Earth[]
First Monster
Second Monster
Contibutor
Light
Earth
TinyDragons98
Brimstone Monster []
First Monster
Second Monster
Contributor
Shadow
Earth
TinyDragons98
Independence Monster Template:AirTemplate:Fire[]
First Monster
Second Monster
Contributor
Inferno
Fire
A Wikia Contributor
Air
Fire
TinyDragons98
Flamegust
Fire
A Wikia Contributor
Note: This monster will take time. The fail times are 23 and 26 hours, so have some patience. Don't quit now just because you can't get one monster. You can do it!