Significance of Navaratri Golu is humbly given below.
Meaning of Tamil festival Navarathri Golu
Golu in Tamil means courtyard. It is an important festival for female. Golu is commenced with Kalasa pooja on the first day of Purattasi Navarathri and continues for nine nights and one day, that is the tenth day called Vijaya Dasami. During Golu days inviting friends, neighbors and relatives to house is the highlight of this festival. Bhajaans and Pooja are performed. Sundal or cooked Chenna, which is a must Prasadam, is given as Prasadam all the Golu days. Among Tamil festivals this Navarathri Golu is the long festival.
Construction of Tamil festival Navarathri Golu steps or Padis.
There is an ethics in constructing steps or Padi for Golu. The Golu consist nine steps or Padi in Tamil. These steps or Padi should not exceed nine. If you wish to keep less than nine steps it should be in odd numbers like 3, 5, and 7.

The philosophy behind the nine steps or Padis for Golu is said as: To worship Devi Durga goddesses, there are nine ways of worship. They are swarnam, kirthanam, smaranam, paadasevanam, archanam, vandhanam, dasyam, sakyam, atmasevadhanam. This concept is represented in nine steps or Padis. The nine steps or Padis in Golu represent nine planets or Navagrahas.

From the bottom to top, the length of the steps should reduce. For instance, from the bottom, if you keep five feet length for the first step or Padi, then the second step or Padi length should be short than the first one and the third step or Padi length should be shorter than the second one and so on and so forth. 
Dolls or Bhommai arrangement for Tamil festival Navarathri Golu
From the top, on the first step, kalasam should be placed. Besides kalasam, God's idols can also be placed. Second and third steps again God's idols should be placed. On the fourth step saints, siddhars and enlighten ones dolls should be placed. On the fifth step noble persons like freedom fighters, philanthropists' and social workers dolls should be placed. On the sixth step ordinary human beings should be placed. Example vendors, farmers, house holders and so on. On the seventh step animals dolls should be placed. On the eight step birds dolls should be placed. In the ninth and last step insects and crawling creatures should be placed. 
The philosophy in Tamil festival Navarathri Golu
In the doll arrangement we can see Gods, saints and great men above the ordinary human beings dolls and animals below them. If, ordinary human beings have good thoughts and does good to others, they will be raised to great men, then to saints and finally merge with God. On the other hand, if they tend to have bad thoughts and do evil to others he will go down to animal level step by step.

The goal of human beings and the reason why we born on earth are evinced in this wonderful Tamil festival Navarathri Golu. What ever situations we are born in, our prime aim should be to merge with God. Navarathri Golu celebration remains us this.

This is the philosophy Navarathri Golu conveys to us. Mind wanders if it is untamed. Through this festival we can tame our minds by devotion to God. In our Tamil culture all rituals are designed in such a way to tame the mind. Let us celebrate Navarathri Golu, tame the mind and attain Thy's foot.

Happy Navarathri Golu wishes.