You can start conquering subordinate cities once you reach level 11 and gain your first subordinate city which is actually on your City Management screen on the far left. You will get Spartacus when this happens. (Well, that's how it used to be anyway. Evony is always changing, but the above is roughly correct.)
Subordinate cities (known more as Subs or Sub Cities) provide you with additional resources. They also provide you with additional troops to fight normal monsters. Therefore, it is well worth acquiring them.
Subordinate cities are either NPC (Non-Player Character, meaning Computer Owned Cities) or they are taken over by players. If a player owns it, the player's monarch name will be on the city followed by whatever the monarch has named their city.
A player cannot launch any attacks from a Sub, so you don't have to worry about someone having a Sub close to your Main City. However, whenever a player bubbles up their Main City, their Subs also bubble. So if you see an unbubbled Sub that means that player's Main City is unbubbled also.
There is a function within each Sub that tells the system to allow troops from the Sub to fight for a player's Main City, and vice versa. If you are unskilled at PVP, change this to option to No, so the Subs do not fight for your Main City and vice versa. The reason for this is that if they are linked an enemy can attack a Sub and not only wipe out the troops in that Sub but also the Main City as well. They will then capture all your Generals as well, depending on how tough they are. So an attack may not even be coming for the Main City but for a Sub, but both will be involved in the fight. If the enemy is strong enough, he will wipe them all out. Granted, leaving them linked so the Sub fights for the Main increases your chances of victory in your defense, if the enemy is not as tough as you. So it is the risk that you run.
You can turn off Sub City fightingin the Sub City Menu, found in the Main Menu or by tapping on the Sub City on your City Management screen. There are check marked boxes that say that the cities will fight for you or not. Uncheck them to stop them from fighting for you. You can do this for select cities only, if you want, by going into that particular city's screen, by selecting the city, and finding the indicator there as well.
Subs can be set to Economy, War-Oriented or Balanced. This tells the Sub to either focus on building troops, War-Oriented, producing resources, Economy, or a mixture of both, Balanced.
Upgrade your Main Sub City. You can do this only for the Main Sub City that is attached to your Main City. To do this, select the Up Arrow icon next to the city's name on the Sub City screen. It costs gems, so keep that in mind. Only upgrade if you have enough gems to spare.
Assigning a Mayoris an important feature to Sub Cities. Mayors are Generals that you assign to the city, and their skills and abilities increase the city's resource production or troop production or both. So having the right mayor is important for each city. Review your Generals and see which one might fit the city most. If nothing else, throw a General on the city if you can, though, because they increase the city's effectiveness regardless of whether they are the perfect match or not.
Each Sub City has buffs. On the Sub City screen, you'll see various buffs. This is what lets you know which Generals to assign as mayors. For example, if my Sub City has a buff for troop attack and trap science, I might want to put a General on that city that complements those buffs, maybe someone that helps to increase those buffs or offset them, whichever I prefer.
The Buildings Tablets you see what buildings the Sub City has upgraded and at what level. It is like a summary screen, so you'll notice that all of the buildings are listed by level. It won't take you to an actual City Management screen like your Main City. You can speed up the current building project by using Construction speedups or you can activate another builder for 300 gems.
Troops Tablets you see how many troops you have built in that Sub City and at what levels. To maximize on your effectiveness, if you notice that your total troop count, at the top is maxed out, meaning you've made the most troops you can make for that Sub City, you can dismiss lower level troops to make more room for your higher level troops.
Abandon City. You can abandon your Sub Cities at any time on the Sub City screen at the bottom left. This will free up a Sub City slot so you can capture a new one. If you abandon your Sub City, you lose everything you have put into that city except the General. All Generals return to you when you Abandon the Sub. However, because Evony glitches a lot, I would Resign your General from the Sub City first before hitting Abandon. To do this, tap on Mayor and then Resign next to the correct General.
To gain more Sub City Slots,you have to gain more Prestige. Prestige allows you to increase your Rank on the Server. To view your Rank on the Server, tap on your Monarch picture on the Main Screen. Tap on Ranking (lower left), then Rank Ranking. It'll tell you your current Rank, Prestige, Weekly Ranking, and the requirements you need to go up to the next Rank.
Often, it is not because of how much total Prestige you have but where you fall on the overall Rank that is causing you from getting to the next Rank. However, it is a circle. Where you fall on the overall Rank depends on how much total Prestige you have. For example, I am currently at 284 on the Server. In order to level up to a Baron from a Knight, I need to at least be 270. The person who is currently at 270 has 143,509 Prestige. I only have 132,342. So although the basic requirement to be a Baron is 20,000 Prestige, I will not become one until I am able to get my Prestige up to 143,510. However, that would only happen if the person who has Rank 270 doesn't also increase their Prestige. So if I really want to go up a Rank, I really need to work hard to build up Prestige.
How to get Prestige. Offer gems as tributes. Also, any time you kill a monster, Boss Monster, farm, etc., you gain Prestige. So, basically, if you want to get more Prestige, play the game a lot more and do a lot more stuff all the way around. As you Rank up, more Sub City slots become available.
