Hi Belita,
Level 23 here...
I don't buy trees and animals, either. They are expensive, and don't give much $ in return; in my opinion, it's because they are supposed to be given as gifts. I don't have very many, because my friends don't give gifts that often, but I'm fine with it.
My absolute favorite crop so far is grapes. You have to be level 20 or 22 to plant them (can't remember which), but they grow in a day, cost only 85 coins, and give you 270 back! Watch out for raspberries; they give no experience.
When I have a surplus of cash, besides expanding, I buy buildings. You get a chunk of experience and earn ribbons, too. Also, the machines are fun, but they run out of fuel quickly, and you have to wait forever for the fuel to replenish itself. But they are convenient when you have enough fuel.
You can't save up and buy the biggest plot you can afford. You have to buy next size in line.

I think the game would be a bit more fun if there were more challenges. Like, if you had to fence your animals in and feed them regularly, otherwise, they would eat your crops or something.
