Clover and milk
You can go to the store (an icon in the bottom row of the toolbox at bottom right) to buy clover seeds, to plant in any empty field then to harvest (four or more hours later, at your leisure) to feed to your cow: one experience point ("XP") for each planting or feeding action - you'll be on level 2 before you've really seen the ranch!
If you want to move ahead fast, harvest all of your clover as soon as it is ready, and replant clover on all cleared fields. But if you have many weeks to fill in, with no desire to spend much time each day on your ranch, you will notice that you get a few coins (up to 190) every day in the "lottery". If you wait long enough and harvest and convert and sell only some clover, you will be able to buy a beehive at level 4 and get more value from all remaining clover and future plantings before harvesting.
Click on each clover field that is ready to harvest. The clover vanishes into your barn and the hovering cursor now shows a "Click to plant" message above the newly-plowed field. When you've harvested three or more fields, click on your cow's manger (the feeding trough) and see how easy it is to give her three bundles of clover, representing the produce of three fields, whisked magically from your barn.
When the cow has processed a bundle of clover, a milk can appears beside her waiting to be clicked and sent to the barn. If there are three cans there, she stops eating and producing, resuming (if any clover remains) when you remove a can or cans.
Milk can be sold, but will be worth more if converted to cheese, as mentioned in the "Cheese Master" section below.
You can send any Facebook friend (whether or not they are playing) one gift per day. At level 1 you can gift any of: clover, tomatoes, wheat. All gifts are free, so it does not matter whether you possess any. Wheat has the greatest monetary value and will therefore probably be the most welcome gift at this level and at levels 2 and 3.
If you have friends playing at higher levels, you can ask them to gift you more useful things:
A sheep will eat your wheat and increase its value by turning it into wool. Harvest it and leave it in your barn while you ask around.