Start matching jewels from the bottom of the board, not the top or middle.
That way you get extra free matches as new pieces fall in from the top, and the bottom corner squares are the hardest to clear anyway.
Save your Powerups:
Conserve your powerups, especially the dynamite sticks and stopwatches, for later in the level when you run into problems. If you have one pesky square left, the dynamite stick is a real life saver!