My army is currently eating over 6 million food per hour, and I'm having no trouble at all feeding them. Between hitting the lvl 3-5 NPC towns, hitting inactive players, building farms and conquering food bonus valleys, and using my gold to buy food on the market, I'm getting along just fine with more than enough food to expand my army further. You just have to work out a strategy that works for your situation, or in my case a balance of different ways to bring in food.