The outfits in this illustration are from the "Clear Card" anime series.

Cardcaptor Sakura characters:
Tomoyo: her dress from Episode 8 when visiting Akiho's house/Eriol's old house
Sakura: her outfit from the opening credits in the second half of the season
Syaoran: his outfit from Episode 5
Yue: his usual costume
Meiling: her outfit from the end of Episode 16

The PuyoPuyo girls are cosplaying as Sakura:
Ringo: the dress that Tomoyo made for Sakura's visit to Tomoyo's enormous mansion in Episode 7.
Amitie: Sakura's frog-themed costume from Episode 3.
Arle: Sakura's "battle costume" from Episode 9 at the aquarium.