Gem Crafting 101 Part 1
Each material has a value for certain stats enhancers. Say, Agility Up or Poison Defense. To gain a Gem from materials, you need to raise the stat above 100. This will ensure a Gem will be created. The trick is to select Crystals and Cylinders until you reach a 100+ value on the stat of your preference. This is a delicate proccess, as when the value is over 100 you can not add any more to it. So it's imporant to keep materials for crafting in order.
Thankfully the game helps you, with highlighting the material compatiable with another material. This means they enhance at least one of the stats of your chosen material. Continue until you’ve reached a 100+ stat and try to not have more than 3 or 4 stat enhancement affected in total.