We can gift you a number of trees. They are free to plant as gifts and can be harvested every few days. We can also give livestock as gifts. They act like animated trees in that they can be harvested every few days.

You can also visit neighbors' farms and do odd jobs for about 20 coins and some XP.

Plowing, planting and harvesting crops are where the bulk of your money and experience come from. Just like trees and animals, there is a time to maturity (T) before they can be harvested. Unlike trees and animals, the crops will begin to wither if left unharvested too long (the maturation time again after maturity, or 2T from planting). They will be completely withered when left unharvested for 1.5x the maturation time, or 2.5T from planting.

The trick is to pick crops that you will be able to harvest between T and 2T from planting. Within that stricture, pick crops that earn you the most per unit time.

Tractors, harvesters, and seeders allow you to (respectively) plow, harvest, and plant 2x2 fields at a time.  They do require fuel, though and come with a fuel tank that regenerates over the course of about 6.5 hours.  They share a single fuel tank with a capacity of 150, and use 1 fuel for each field serviced.  Fuel refills are available for purchase, but require "farm cash" which is purchased with real cash rather than coins, the main currency of the game.  The refills are single use, not refilling extra gas cans.