Your Santro has GENERAL 155/70 R13 tyres as standard. They are very poor quality, available from AutoExpress for only Rs1200 per tyre.
You need to go for a better brand, and a grippier size, whilst retaining the overall diameter within the accepted specs of the car.
That Size wouldbe either 165/65 R13 (GoodYear is nice in this) or 165/70R13 (Bridgestone B700 is the best).
Depending on what you go for the price will vary from between Rs1800 per tyre to upto Rs3000 per tyre (185/60r13 for e.g.)
As soon as you change tyres get your wheel alignment checked - we have one of the most sophisticated 4 head laser machines in the country.
After that you'll feel a MAJOR difference in grip.