The CircuitPlayground and CircuitPlayground Express are great boards for learning with. This is largely due to the abundance of sensors and actuators built into the design.
While there is a pile of builtin hardware, it doesn't include everything. Fortunately it does have several useful connections run out to the alligator clip pads around the edge of the board. That means you can connect to it using alligator clip jumpers, like one of these:
This can be great for a quick & dirty test, but isn't very robust. I got to thinking about how I could deal with this and took some inspiration from some Micro:bit products I've seen. My solution: a series of shields that bolt on through the clip holes.