First board: If you have the opportunity to use the given Color Burst immediately, do it. It'll help a lot. Cool down all lava blocks as soon as possible. You should leave the level with at least 6 toys. Of course - as fast as possible. And don't use the Magic Orb!
Second board: Use it at the very beginning here, the best on the colors which are the most present on the toy-tiles. Take the short way to the exit, cool down those lava blocks as fast as possible and get to the next board with at least nine toys.
Third board: Bring the water to the lava blocks fast. Then, don't care about the water! Just make big combos around the toys-square, but keep the Magic Orb until you have no other move at the toy blocks. You should be able to get enough toys if you haven't spent a lot of moves on previous boards.