Some units/factions tend to have more stamina than others. Also being in combat tires your troops. Its definitely worth paying attention to.
As for income, there are some good guides around the forums if you search. General consensus is:
1) Low tax rates everywhere. Yes, this is counter intuitive, but it helps your population grow quicker, allowing you to upgrade cities sooner and thereby gain access to higher level economic buildings. It means your income suffers at the start, but means your income should be better later when you need it more.
2) Focus on building economic buildings first. First level of roads are a must (also helps units move around quicker) and then other farming buildings and stuff.
As for not seeing things on the map, take a general, and have him walk around your territory building watchtowers.