Count relationships rather than decorations
The appeal of Sweet Merge Puzzle is the progression from small candies toward more elaborate treats. For planning, however, the important feature is which visible candies match. A newly evolved sweet changes the set of possible partners around it. Notice that change before making another slide. The picture is attractive, but the matching relationships explain why an apparently small move can alter your next available decision.
Ask what the merge leaves behind
Imagine that two matching candies combine while another candy of their old type remains elsewhere. The new treat may be useful, but it is no longer that leftover candy's immediate partner. This hypothetical illustrates why clearing an attractive match and improving the overall arrangement are not always the same thing. Look at both the created sweet and the candies that no longer have the match they previously appeared to have.
Learn the actual sliding behavior
The supplied record says to slide and merge matching candies, but it does not specify whether every piece moves together, how new candies arrive, or what ends a run. Establish those rules from the loaded game before applying a familiar strategy from another merge puzzle. Then review the visible inventory after each upgrade. A good next move depends on the new relationships on screen, not just the size of the candy you last created.
Puzzle
A merge removes one kind of matching opportunity while creating another, so reassess the sweets after each combination.