check your trade strategies. for beginers, the basics of low water, 1 gm, and buy 10 will be fine, with all but your military items at 120 quality. also, even if you have no military, you might be buying some anyway. you can look at that in the trade strategies.
even if everything is correct, it is normal that your population requires more supplies, than it pays for. this can be excessive if you gained allot of population, as your country will have to buy up to its new level. even still, it is normal for countries to make less money than the financial pages says, as they buy supplies for the population. their are ways of goofing with that. i'd suggest trying different salary levels.
but i'm not sure it is that, or the corp selection, ei the type of corps you set up. haven't gone that far playing with it yet. but it seems that depending on your salary levels, and worker types, that your country needs change slightly. but thats more of a theory
also, if you've set up purchasing contracts from your own corporations, that could do that to. you can check your country contracts under trade.