GEARS
SPINNER
RAMP
Tunnels
Cardboard Tubes
Half Cardboard Tubes
Wall Maze
Make sure to have wide strips
Windmill Obstacle
You could place this element perpendicular to the obstacle or in the same direction as your ball course
Inclined Planes
Add pins to secure the ramps, you can add triangle support at the center of the ramp for support
Funnel
Cut the end
You can use cups as well!