I know you're in India but do you have access to a site called aliexpress? This is a seller portal site except that most sellers are in China. Generally used parts are sold on this site.
From May of 2017 to around June of 2018 Crypto Currency mining put a massive strain on the graphics card market because people were buying whatever they could to mine Altcoins. Around August to September of 2018 the value of Bitcoins and all the other Altcoins took a nosedive, and then a majority of the people who were mining sold off their equipment. Both versions of the GTX 1060, GTX 1070, RX 580, RX 480, RX 570, and RX 470 were all popular mining cards. You can find these cards for much cheaper then their MSRP price on the 2nd hand market. I can usually find a used RX 570 for 5500-7500 on ebay. For 13800 INR, I can find a used GTX 1070 which would be a lot better than any of those cards.
Also, the Crypto Currency mining glut caused Nvidia and AMD to over produce cards, which is why there are still GTX 1060 cards on the market. Both versions of the GTX 1060 were replaced by the GTX 1660 and GTX 1660ti earlier this year.
The RX 570 is a little bit weaker than the 3gb GTX 1060, maybe 5% to 10%. The only exception is the RX 570 has more VRAM which is helpful in a few games. 3gb of VRAM is too little for the GTX 1060.
The 3gb GTX 1060 will do fine for now but you'll probably have to upgrade it in a couple years.