Collect most toys on the last board. Before, just take what you can't avoid ;-)
First board: Collect the toys at the top right and top left corners first. Then collect the rest of the toys on the board (the ones positioned on mud blocks). Look for combos to do so. Afterwards, proceed to the next board as soon as possible. 13 toys.
Second board: Go from the bottom to the top. Match some combos to collect the toys (all of them, if you can) and make sure the flow of water doesn't reach the exit before you've collected all or most of the toys on the board. 8 toys (total 21).
Third board: Collect some toys (the ones you can) and make sure you proceed as soon as possible. You could have difficulties with breaking the way through - feel free to use the Color Burst to help you with the exit tile. 8 toys (total 29).
Fourth board: There are a lot of toys here. Try to get a good amount of them before opening the path to the exit. 26 toys (total 55).
Fifth board: The color bursts and line blasts should make it easy to collect the remaining toys. 54 toys (109 total).