Now that you understand the best stats for each of your builds, gems should be pretty easy to understand as well. You should always gem for your most important basic or advanced stat. Ideally every gem will be the same other than your meta gem in your helm and enough other gems to meet its requirement. This means that for most slots you will not be matching the slot colour. This is important to understand, since many wow gold players think that they must follow the slot colour and therefore hurt themselves by not getting the biggest benefit possible.You should be gemming and enchanting for hit and expertise until you reach the caps and then focus on Strength. If you are still leveling just focus on Strength. The best meta gem is a Chaotic Skyflare Diamond since it provides crit and a causes all critical hits to cause more damage.You should gem and enchant for Defense until you are defense capped and then for Stamina. For Defense this means either yellow "Thick" gems or green "Enduring" gems until you are capped. When focusing on Stamina it will be "Solid". As a Tanking Death Knight the best meta gem is an Austere Earthsiege Diamond which provides Stamina and increases your armour value. Enchants are much the same as gems. Focus on the stats that are best for the type of Death Knight that you play and you should be good.A very important thing to remember with both gems and enchants is that each time you get a new piece of gear your balance will change.