Right now I find it very difficult to understand at a glance where my money is coming from.  The kingdom report breaks income out in terms of *type* of source, but it still means I can't tell exactly which city is making the most of any resource (especially with the influence of caravans, which I don't fully understand anyway) without clicking through all of them and trying to figure out exactly what's going on with that city.  So perhaps in the tool-tip that appears when you hold your cursor over your current gold, it should break out your income for any resource by city.  This is basically the approach Sins of A Solar Empire takes, and I find it very useful.