Here are some tips:
1st: Don't grow food on your own.
It is not recommended that ''small'' nations (small meaning new) grow food because it isn't practical. Instead of investing your precious improvements on farms, invest them to mines. With mines, you can get resources to make power stations and more. If you think you have too much of a certain resource, try trading it for money on the trade section in the game. Of course, you can't let your nation starve, so with the money you got from trading, purchase a few thousand food.
2nd: Join an alliance.
No nation in Politics and War can become self sufficient, because no nation can get all of the resources by mining them. Of course you can get any resource you want through the market (Trade section) but that's impractical, and you can lose money REALLY quick. One way to get resources for cheap or for no price at all is to join an alliance. There are many alliances in Politics and War. Just go to the alliance recruitment page and find the alliance you want. It might be hard to find an alliance these days due to the Global War, but there are some that aren't participating.
3rd: Raid.
Raiding is one of the most sufficient ways to get resources of any kind. Of course, raiding requires you to build a military, so don't forget that. Just make sure you don't raid the wrong people that are backed by an alliance, or you can say bye-bye to your nation.