WASD to move. E to interact. What to do: If you are touching a plot of land that has no seeds in it with seeds, then you will start to grow wheat. You'll definable notice it. Once the wheat is finished (you'll know) head on over to it and press e. Once you do, you should get one wheat. Head on over to the truck guy to sell your wheat. Press e to sell it. Once you finish selling it, head on over to the store. Press e to buy something. he will ask you if you want seeds or fertilizer. You can say 1 or Seeds to buy seeds, or 2 or Fertilizer to buy fertilizer. If you have multiple wheat or multiple dollars, you'll have to buy/sell them separate.
Dunno, just came up with it. Kind of reminds me of my hunting game thing I came up with a while back. BTW, seeds cost 5 dollars, and fertilizer costs 50 dollars. If you want to buy fertilizer, then make sure you have 55 dollars, because nothing is worse than taking all that time to buy fertilizer, then realize your broke therefore can't use it.