Hi Manimegalai,
DA and HRA basically depend upon the employer. There is no rule to fix DA and HRA. However, fixing DA should be higher than the minimum wages act based on the particular state and the place. PF is 12% on Basic and DA, where the 12% can be on the full Basic and DA or it can be limited to a maximum of 6500.
Gratuity will come into the picture only after completion of 5 years of employment. There is no need to bother about it now. Even then, it will be 15 days per annum of the last pay.
For any more details, you can reach me.
Cheers,
Jeeva
9343753361