(my Atlantian Castle is upgraded to Level 6, but no Queen Samera yet, don't know if that matters though)
I did do non-stop Toadstool Forest Adventures from the moment I found out about them, so it wasn't quick (but well worth it )
Good luck to everyone still trying to get one! There are still 6 days left, don't give up.
Even if you don't need the event supplies anymore.. the cost of the Toadstool Forest Adventure is not high, so I think it's worth continuing.
It doesn't cost a Golden Nugget each try at least.. we don't get this opportunity each event