Owning areas/ Cutting corners
The final quest for bananatic was owning 4 areas for me. (not sure if its the same for everyone) before that one is population and I think the first was getting to bronze age so, although one of the quests within the game was to own my first area I had totally ignored that side of the game until the final quest came up.
In your selected army you can have 8 units to go to battle with but there's plenty of room to store more. Fill that room up while you're doing your first quests that way once you go to the map to dominate the areas, you can switch out the injured ones while they heal ready for the next battle and replace the dead ones allowing you to dominate and own that part of the map without going back to the city.
Then you need to scout the next area which takes 6 to 7 minutes on the first few, giving you a little bit of time to go back to the city and make more to replace the dead.
On a side note, the slingers aren't massively important to the battle you can get by without them for this quest (their attack is 6 and their defence is 3 whereas the spear fighters have 7 in both) but they are ranged fighters which can come in handy if you're having a bit of trouble winning the battle.
Anyway, that's what I'd do if I had to start over again, maybe most of you pay more attention than I do. but I hope it helps someone about to start the game.