Only 4 gems drop per turn, so you need to make small matches of 4 or less or the board will empty out and you won't be able to reach those pesky clouds at the top!
Each cloud requires 3 hits to destroy. While the level starts with a generous allowance of 7 spins you will need to supplement as many free spins as you can get.
Dev tips:
Try and avoid the buildup of large sections of a single gem color. Break up large blocks by matching gems of a different color across their path.
Minimize board reduction by making matches inside existing chains rather than extending them.
Place normal gems over boost gems to avoid them taking out large sections of the board.
Use shifters to move gems into a desired reel slot, especially if you have only one cloud left to break!