How can I become street smart in India?

I'm too nice to my own detriment. It's super easy to bluff or con me and I've gotten remorseful of being raised too nice, doormat-y. And this is going on even in my 30s. I have realized most people are manipulative and will take things without giving anything in return. For example, I caught the petrol pump attendant conning me of 50 rupees and despite confronting him and him agreeing, he managed to screw me up. Sorry for the resentment but here's my question. How can I become street smart here? I just want to go about living my life without being screwed or manipulated by anyone else.