Your priority on the level 57 is clearing the path to the flowerbed.
1. Concentrate on the matches/explosions near the flowerbed, leaving the single chained elements to be cleared by explosions and auto-matches. Each 3 matches or explosions next to the flowerbed make it produce 4 flowers on the field. 2. Explode several power-ups at the same time, as it will allow you to get the Rainbow Blast faster. At times, it’s best to activate the Rainbow Blast on the pieces that are less present on the field — it creates more opportunities for larger matches, and thus more power-ups. 3. Try to focus not on collecting, but on creating new flowers. Sometimes it’s easier to get them using a Rainbow Blast or auto-matches.