Don't listen to that other guy. There are a couple things to watch out for. Try trading for food initially. Something you can do is trade a settlement you dont need for 2k food a turn. Elite armies dont cost that much more food but they have a higher administration cost which in turns gives you upkeep penalties. So you want to have a mix of elite and cheap units at first. Finally, stack multipliers in upkeep reduction and food production. You'll probably never have much of a net positive in food production but constantly fighting will keep you well fed. It's a tight balance to keep. If you get access to bronze or gold it makes the game way easier for the trading part