In that case, a purely manual flash might be the cheap, if inconvenient, way to start. The only problem there is that you may be turned off by off camera flash because of how unreliable and cumbersome that particular model is to use, not because you don't have a use for it.
If you are willing to invest in a radio controlled setup, Yongnuo and Godox are the way to go at the budget end. Neither are officially available in India, as far as I am aware, so you are at the mercy of seller 'warranties'. They also seem quite expensive here, compared to the US (judging by the price difference between them and the Canon flashes).
In your case, you will have to find Sony compatible flashes which may take a bit more digging. Also, check if your body supports high speed sync and second curtain sync before investing in a flash and trigger that do.