This one is achieved by getting twenty bonus items. Bonus items are the treasure chests, boost, magnet, coin bonus and any other thing you see floating in the game. However, it won't be unlocked as soon as you have collected 20 bonus items. It should show up as a mission for you to complete. Complete the mission and the achievement pops. Can't say if there is an exact time for it to show up, mine showed up while I was on level 7.
Hope this helps.