Been playing a lot of Civ V recently, I suspect I have much still to learn.
1. In terms of strategy, do people tend to limit their number of cities, have certain cities focus on specific aspects such as science?
2. I ask about focus as I was playing a game the other day, while I noticed I had way more gold than the other players, their gold per turn was like 6 times more than mine.
3. Is gold per turn or maintenance just reduced by units and buildings?
4. Having lots of fully upgraded cities seems to be a route to bankruptcy.
5. I also noticed the more cities you have, the more unhappiness and less culture is generated.
5. If I want to expand an empire, how do I avoid the costs associated with that?
6. You build a constabulary then police station, does one replace the other or do you need to maintain both?
7. Is it cost effective to upgrade a unit through the years or simply buy or train a unit at a higher level?
It's a bit late so you might have the answers now but since I came in here to let everyone know the Civ 5 series and all the DLC's are on offer this weekend at Gamers Gate for 50% off, though I'd answer these whilst I was here
1. I tend to go 3 cities as fast as possible. It puts me into a position where I can transition into any type of win condition, such as I can stay with 3 or maybe push a 4th and go for a Culture victory, or continue expanding for a Science victory, or work on my army more for a Domination victory.
2. Gold per turn is so varied I wouldn't worry about it, other players might have been in a golden age, or they might have sold their luxuries for GPT or may have lots of units they have to maintain.
3. Yes, possibly wonders too (thinking Big Ben).
4. If you build everything, then yes definitely.
5. You can sell spare luxuries for gold per turn (I normally do 83 gold up front and 5 per turn for 30 turns per luxury). Otherwise, you'd have just to make buildings that produce gold. You could also set another city to gold focus and/or set their production to wealth to help with the costs temporarily until the city finds its feet.
6. You maintain both, but receive the benefits of both.
7. It really depends on the unit, and how fast you can produce units from a production city. If I can turn out a Gatling Gun for instance in 3 turns, then I'd probably not spend the 220 gold to upgrade a Crossbowman in one and instead just replace it with a fresh produced unit. You have to take into consideration the units promotions though, and also when the unit is a UU. Some units I tend to always ditch and make another one though unless I have massive gold per turn, such as Caravels into Ironclads (which is about 260 gold I think?).