Go to your right (as you face the main entrance of Hogwarts) and, in the portico, triple-cast Depulso at a block in the wall furthest from the main entrance. A Spongify tile will open at the other end of the portico.
Bounce up to a loft and run quickly to the other end to score four cauldron cakes and a collector's card (#12 purple). If the floor opens before you reach the card, bounce up and try again.
Up near the badger stone, Alohomora the banner and then cast Lumos on the gargoyle.
Quickly run back to the bridge that leads out to the paddock and cross it to reveal two secret alcoves with gold chests (Fifth Secret).
After collecting the treats, go back and cast Lumos on the gargoyle again. This time, run back and go to the right side of the main entrance (as you
are facing it) and find a hidden Spongify tile.
Bounce up to get a collector's card (#11 purple).