First off everything you need to go to the 2-10 level becouse it is the most easy to get this achievement of all levels , so when you go to 2-10 you need to get 30 coin in a row (the 30 coins dont need to be 30 on your screen) you need to get the coins without any disapear so the achievement is over , the fastest way to get it is killing ordes and planting grave busters in the graves so after this you might have the achievement , good luck :D