Parade float spot is not a bad idea at all. I spend my on accidentally clicking on purchase the floats. I use gems on special event gem characters. They usually seem to do a good job helping with the special event. This includes Frozone, Zero, Olaf, and Sven.
I buy characters. I've bought the special ones that go along with the special events. I also bought Merryweather because I wanted to complete the fairy set, and Pluto because I thought Mickey might be lonely without him. I also bought Pluto's doghouse. I have bought one extra chest spot, too. I also have bought a few of the attractions.
I’ve played a ton of resource management type game and this is one of my favorites. I always invest “gem” type currency on long term. The first items i saved for were the extre chest slot and floats(plus spaces). Even though its not as fun as grabbing pluto first i feel it gave me a much better start in this great game