Sonic Speed Simulator - Limited-Time Halloween-Themed Sonic & Friends plushies
Source : https://twitter.com/SonicSimulator/status/1584917255950835713
Gothic Amy is perhaps the most difficult for F2Pers given you need to get back on Sonic Speed Sim every four hours to get 70 "candy" or so. I already purchased Gothic Amy but right now I'm saving up to buy four more golden pumpkin chao for evolution.
Witch Amy is not that hard to unlock given she was part of the major event. I unlocked her in under a day or so.
Vampire Sonic is a bit more challenging given you need the patience to go back on every 24 hours to unlock. The last challenge of 250 sky hoops is not that bad, especially if you saved the "10 seconds sky hoop" power-up from before. But I find Tornado Assault a good way to get plenty of sky hoops.
My only concern for unlocking characters or chao I want is time vs F2Pers. If I had Robux I would of purchased those golden chao by now, but given I can't all I can do is check back every 4 hours to get candy and hope I'll get enough to evolve my chao before Goth Amy changes her stocks.