Building Gems

Gems are one of the many fully customizable aspects of this game. That being said there are a lot of wrong ways to do it and really only a few right ones. Firstly I should give this information

Garnet=hit points
Ruby=physical attack
Sapphire=magic attack
Emerald=physical defense
Agate=magic defense
Opal=physical critical hit rate
Spinel=magical critical hit rate
Amethyst=mana
Lazurite=damage increase
Moonstone=chance of suffering crit reduced
Now that you know what they all do, let's talk about how to build them. At level 6 gems they can be fused together to give you double the gem effect, this is where I would like to begin talking about them. You can only have one of each dual gem per each piece of armor. You cannot have two patk/pcrit gems in the same piece of armor. This imposes certain restrictions on you in the way you can maximize the effect of these gems. These are referred to as gem builds.

Full damage gem build
Basically this build requires the maximum amount of rubies/sapphires. You will need 4 per each piece of armor. You would fuse the gems together as such: atk/hp atk/crit atk/pdef atk/mdef. This will maximize the amount of attack power you have and give you the most damage output.

Full defensive gem build
This build is not very popular as most classes just aren't effective in it. Basically it's fully balanced in the way it's built. It looks like this hp/mdef hp/pdef atk/mdef atk/pdef. This build give you twice as many hp gems as any other build and also doubles your defensive gems vs the offensive build.

Hybrid gem build
This one is my personal favorite. It consists of high def and maintains most of it attack.
It looks like atk/hp atk/pdef atk/mdef mdef/pdef. You still get the double effect on gems, and you keep 75% of the attack, the only thing you short yourself on is critical strike rating which most classes have very high amounts of to begin with.

Many people use one of these three builds for gems, the ones that don't are known as scrub builders :)

8.0 has released lvl 85 or t4 armor. This armor has 6 slots instead of 4 so a few things are now viable. the use of matk/mana and matk/mcrit can now be used in every piece for casters. patk/mana is not great but it does add an extra ruby to your set. the mdef/pdef gem should be present in every piece of gear once you get into this new armor.

9.0 Lazurite,moonstone,diamond are now readily available making them the most important gems to get. You will will to fuse these with the attack gem for your class, either ruby or sapphire. Also gem vessels have been introduced. They fit into a gem slot like a normal gem, these are fully customizable and upgradable however. You use gem vessel molds to level it up which increases the amount of slots and limit of each stat. Basically you put gems into it, if it's the first gem of a certain type it will take a blank slot and begin leveling up, not guarnteed though. Basically it works like armor leveling, it has a lucky bar and the higher it fills the better chance it has of adding the stat. What I have found thus far is to use your lower level gems to get the bar up and then use your high level gems for big increases. The gems you put into it are up to you, don't fill a slot with a gem you can't afford to keep putting into it.