Get addicted to this game. The more you play the faster you will max your rank. (The maximum is 30 by the way.)
Complete goals. Completing goals will give you the secret weapon to levelling up. XP. That will increase your level meter. You can increase the amount of XP given by upgrading it in "My Stash".
Carry your game. Bring your device to work if you can. Then you can play while break time and can level up faster.
Bonus level 5
In this level try going through different colored hoops to get different challenges. The easiest ones are the green ones.
Farming gifts
Go to Viewpoint Hill level 8. Keep crashing frisbee before you get through first tube, until you see a gift right before it. When you see it, collect it and crash into tube. You will be able to open it. Touch the world view icon that allows you to see all ten levels. Go to ten. Immediately hit pause, world view, then go to nine. Then hit pause, world view, and go back to eight. Gift should appear in same place. Repeat process to get easy gifts and rack up your inventory!