As an early player, Pluto and Pluto's Dog House are cheap and help with magic collection and tasks. Otherwise, try to keep a stash of gems for limited time events. Lately, we've needed 180-200 gems for 1st character, 250 gems for 2nd character, 50 gems float 150? for special building (not sure because I don't usually have enough gems to afford the special building). When you get farther into the game (way farther) Aurora's Spinning Wheel and Merryweather are also cheaper and useful. Otherwise, it's about what characters you can't live without. Rex, Maximus are generally considered more useful than Boo or Wall E. But for those of us who aren't spending real money, by the time we collect enough gems to get a premium character, we've already collected all the tokens they drop.
As for parades, yes, they do drop gems, but not everyday. In my IOS game I opened 4 parade spots, in my Windows game I only have 3. I swear, I get more gems from only having 3 spots than 4 even though when the game was launched they said that longer parades have a better chance of items dropping (but maybe they meant tokens, and not gems). I have 2 platforms for chest openings. I do not buy chests, gems are far too precious. But I have all the limited time characters, so that limits the usefulness of the special chests a lot too.
