You're out of magic? I'm curious to know how you've built your park. Did you place the rides in nice places with decorations surrounding them? I've collected almost enough tokens to unlock Fauna but I have enough magic to buy multiple pieces of land for 75k. I'm not going to have any issues running of magic unless things start costing 500k or something.
At least for me there's no real secret. Just have as many characters as possible, do the tasks as they're assigned, do 1-2 hour tasks when I'll be active, switch to 4 hour tasks when I won't be able to check in, and finally queue up 6-8 hour tasks at night before bed. The other character I don't have that is unlock able is Mother Gothel. Everyone else is pumping out tasks whenever possible.
Just spent 85k to clear off the land near Its a Small World that will open up Mother Gothel quests last night. Went down to 240 total magic left. Wake up this morning with approximately 12 hours left on the 24 hour time and back up to 17.5k magic.
OK, I'm pretty much doing everything you are (the quests, shorter activities when I can play a lot, etc.). I don't have all the characters. Never bought Zurg, Wall-E, or Boo because I don't have the gems for them. Waiting to welcome Zurg, Donald, Eve, and Mr. I. and my magic is not building up fast enough for all of them, plus the lands by small world (3) I will need to buy. Plus I need to spend a bunch to level up my characters. It's never enough!