I way overvalued Iron and Irrigation when I first started playing. At first, I was all, "OMG! If I don't get these advances, I'm going to drown in corruption and be unable to do anything!"
I've learned that while they are very useful in maintaining your civilization, they aren't the end-all. It's possible to wait for the Age II advances. The upgrade from Age A to Age II mines/farms is not pleasant, but it's doable, especially if you snag an Efficient Upgrade or two. Having only the basic cards in Age III would be ugly, though. I don't think I've played a game like that. It would be difficult.
Another thing I've learned is how to use yellow cards to manage your action pool. Efficient use of actions: Rich Land, Ideal Building Site, Breakthrough, Frugality. These cards allow you to save resources (note lower case) while advancing your civilization in some way. Inefficient use of actions: Revolutionary Idea, Bountiful Harvest, Mineral Deposits. These cards give you resources, but you need to spend another action to do something with them. That's not to say I won't play them, especially if I have a Republic, but I keep in mind that I need two actions to accomplish my task instead of one.
