If your priority is unlocking the triplets you best way to go about this is this way:
1) the first triplet is the red one. you receive the curio shop and have to unlock the red bimbette (it is also the first chapter of the event)
2) while unlocking the red bimbette best collect chocolates for 2 carts (about 5k-6k chocolates)
3) you earn chocolates by flowers that appear every 30 minutes (5x 13 chocolates) and by different characters and buildings
4) once the red bimbette is unlocked you proceed with her tasks (there are 2 chapters but don't worry the tasks are short)
5) once you finish chapter one of the event you receive the fashion boutique (together with the green bimbette) as a reward
6) once again you unlock the second bimbette
7) while unlocking her you best collect chocolate for the butcher shop because it is needed for one of the task of chapter 2
8) after finishing chapter 2 you receive the yellow bimbette that you have to unlock (chapter 3 unlocks in 2 days)
9) decorating the buildings and collecting items for the new dresses are side quest and you don't need them in order to finish a chapter
I hope it helps
good luck!