Not a hard game to understand; but it can take time to build up a decent empire.
The basics:
cities: They generate income through taxes. You control the rate of taxes through them. Depending on how much, or how little, you tax, it determines the overall happiness of your empire. The happier your empire, the higher attack % bonus you get when defending or attacking. Taxes are collected through the number of turns you put in. The higher the city level, the higher the population. Additional cities stack. Cites are the only buildings that can be rebuilt by turns. If all your buildings are destroyed, using turns to fix your cities are the only way to rebuild your empire from it's ashes. You can also steal money from rival cities, as they can from yours. The level of cities determine how much.
Barracks: They are used to hire and train your warriors. Use turns to hire and train them. Warriors can be trained up to level 9 - they can also gain levels through battles. Barack levels determine how many warriors you can house at anyone time. Warriors are depleted when you attack other empires, or they die in defense of your own.
Armory: They are where you buy your weapons from, for your warriors - you can lose weapons in battle in other empires, or gain them when enemies die attacking yours. The higher your armory level the better weapons you can buy from them. You can also attack your opponent's armory for a chance to steal weapons from them. The higher their level, the higher weapon level you can get - likewise, if they attack yours.
HQ: You need an HQ to attack other empires with. The higher it's level, the more warriors you can send to attack your opponent's building.
Spy Hub: Before you attack other empires it's always good to see what buildings and defenses they have. This is what a Spy Hub does. You can also sabotage your opponent's defenses - but this seems to be random. I believe that the chance of doing this is based on your level and theirs. You can also steal intelligence points, as they can from you, but I'm not sure what they are for yet..
Strongholds: These are your defenses. They give defense 5% on all buildings they cover (10% on themselves), and they can cover up to four in a cross like section. If they overlap other stronghold sections they automatically stack, giving you a higher defense %. The higher their levels the higher defense % they give. You can reach a maximum of a 100% defense.
Launch site: Ultimately, this is the main goal of the game, and something I'm not quite sure i understand yet. I believe that it is based on how many of these, and how many research points, your site has that determines the winning site. You can steal research points, and they from you, from attacking these buildings. Once a winning side is determined, the game resets - on research and launch site points, not the entire game.
other stuff:
You earn 9 turns for every one minute of real time. They stack to a maximum of 300. You don't have to keep playing the game to earn them. If you leave the game and come back, at a later time, they will stack up to a maximum of 300.
You can only attack empires from rival sites, none from NG.
You can build places to farm points and money on rival sites, if you have an account on those other sites.
Strategy:
I'm not sure how others do it, but I build cities first for the money. I don't play with the launch site till I have everything built up to a significant level - that being level 9, at this point. I place the cities on the outer most areas, then place strongholds next to them. Everything else i place around the center. I also had an armory, but since sold it, after it was destroyed - I have plenty of top level weapons from those foolish enough to attack me. I plan to put the launch site in it place, after building everything up, and making as much money as i can with cities.
http://tempupload.ngfiles.com/3656365.warofweb.jpg
One last tip, spend you money as soon as possible. Money attracts unwanted attention.