You need:
Construction adhesive for any materials, for example Pattex or Lugano. If the Sphere is intended for outdoors, the adhesive should be weatherproof.
For the construction of a sphere of 68 cm diameter:
24 Pieces Flower pots 16 cm
20 Pieces Flower pots 12 cm
10 Pieces Flower pots 10 cm
8 Pieces Flower pots 8 cm
8 Pieces Flower pots 6 cm
moss, succulents or plants for decoration