If you do not have enough resources, then you will have to wait. Also, research other stuff that are good to, like Gold Mining and Stone Mining (Stone Mining should be researched later unless you want a castle as the "2" buildings).
 Universities should be built first because they have fairly priced but powerful upgrades. Monasteries should be built later in the game unless you are planning a siege in the early Castle Age. Continue to create villagers, and research Wheelbarrow or Town Watch (Wheelbarrow may be too expensive, but do not use your food on Town Watch of you have less than 100 food). You must build another Town Center though. More villagers = more resources = better military = better chance that you will crush your opponents.
 Build a Barracks, Archery Range, Stable, Siege Workshop, and other buildings. The order is listed below.
Barracks
Stable
Siege Workshop
Archery Range
, You should have 4 military groups. Continue to build up your military slowly, but DO NOT FORGET ABOUT YOUR ECONOMY!!! If you forget about it, you will not have enough resources to build up your military, well...you will lose. Keep creating more villagers until you think the mark reaches 50 for villagers and 50 for military units (15 infantry, 15 archers, 15 cavalry, and 5 siege units).
 This will make it easier, as the economy will boost, leaving you with many resources for the military. When you reach 1000 food, 800 gold, and a castle or 2 Castle Age buildings, you can choose to advance to the Imperial Age and continue to work on your military for an easier win. Or, you can lead your military of 50 troops (it is actually a lot in this game) and destroy everyone. You should advance to the Imperial Age if there are more than 2 enemies, and just attack if there are 2 or less enemies. If you are planning to do the military attack, go ahead and crush everyone. If not, here is what you do in the Imperial Age.
Immediately research Heavy Plow and Bow Saw.
Build a Monastery and a University.
Build up your military.
Make the infantry in one group, the archers in another, the cavalry in another, and the siege units in another group.
Do the economy stuff before the military stuff.
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