Set the map bigger, that'll give you more room to work. Also if you find resources hard to find start doing adventure tech research, one of the options makes extra resources appear and it helps a lot.
Finally - just to be sure, you are building the farm upgrade on the fertile land tiles (and other upgrades on their tiles) right? You'd be surprised how often people don't realize that you have to do that. (Click the fertile land once it's in your city bouandry and click "build").
If your armies are in trouble, make sure you're doing warfare research for new equipment and squads. Then when you go to train units, you can design ones that use new weapons and are stronger.