FarmVille addict here
I'm on level 40, have a chicken coop full with 60 chickens, 2 full dairy farms, a full stable, a completed maison, and have mastered:
-soybeans
-wheat
-red wheat
-eggplant
-bell peppers
-artichokes
-grapes
-cotton
-cabbage
*Tips for earning more XP*
Plant a cheap crop, like soybeans, that earns XP. Then instead of waiting to harvest, delete, and replant. Repeat!!
Buy expensive items in the market (ie houses)
Work on crop mastery, plant (and harvest) crops you've mastered for bonus XP
If you have FarmCash, usually when you buy a mystery box or crate you will get a decent item.. I've gotten a Bed & Breakfast, Shamrock gazebo, Acai tree, 2 lakes, a mini greenhouse... PLUS coins & XP usually
Complete requirements for awards
Complete collections
Help your neighbours