Gold is, arguably, the most important resource that you are going to come across in this game. While often you start off with one nearby, gold eventually runs out, so there is a "time limit" on all games in Warcraft because of it. However, usually it takes several hours for all the mines on a field to be overrun, so don't worry too much about rushing around and doing things. When it comes down to it, it's also the resource you are most likely to run out of. To gather gold, you have to be near it for most of the species.
 Gathering Methods By Species
Humans need to build a Town Center near one, as do the Orcs. However, the Undead only need to summon it, a Necropolis does not need to be near by. The Night Elves need to be near as well with their main building, the Tree of Life, but they also have to wait for the tree to grow into the vine. For the latter two species, the minions do not have to run back and forth with gold, but can stay there. It's automatically added to the stockpiles. As seen above, this gives the undead the best advantage. It's also important, for this very reason, that you choose to expand. You can manage to win the game without doing so, but it will be very, very difficult in some cases if you try and take down all the enemies with roughly 13,000 gold available.
The maximum limit for gold gathering for both the Undead and Night Elves is five. For Humans and Orcs, more may be used, but if you place the building for gathering gold close enough, any more then five will not increase gathering efficiency.
 Effects of Upkeep
When you begin to build a large army, you will notice that it will take a chunk out of your upkeep at predetermined points in your army's growth. Be sure to use your army when you get the chance -- when you are at full upkeep, with only 3 out of 10 gold actually going into your coffers, you are loosing a massive amount of money each time you just let units hang around. If you have an army sizable enough that you feel comfortable charging out into the plains of battle, do so!
 Methods of Gathering
Gold can be gathered in a variety of methods. It can be gathered by the most effective manner, which is mining it. You may also sell items found by fighting creeps or simply found on the map, or by finding Gold Coins.
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