Kolu's custom is to start with reptiles and parapanas and move upwards as animals, humans, sages, saints, siddhas, devas, avatars, triads and triple goddesses.
The living organisms like tree, plant, vine. You can put toys of plants like grass, plants, fruits, vines etc.
The amphibians like snail, conch etc. Sochis and toys made from sochis are placed.
The toys of three intelligent creatures like ant, termite, small insects and earthworm should be placed.
Place toys of quadrupeds like crab, beetle, butterfly etc.
Five sentient beings such as birds, animals can be placed.
The puppets of psychics should be placed. Toys like leaders, achievers, wedding sets can be placed.
Dolls of people who have risen to greatness from people like Ramana, Vallalar, Vivekananda.
Dasavathara, dolls of Ashtalakshmi, Devas, Navagraha lords, Indra, Chandra can be placed.
Statues of Brahma, Vishnu and Shiva seated with the goddess should be placed on this top step. You can also place a complete Kalasa Kumbha. Along with this we have to put the Pilliyar toy or idol.
In this way the toys should be arranged and placed in each level.
I have been keeping golu for the past 26 years.