Oki, let me give you some pointers..
1. Your petrol economy would increase about 10%. Even more depending on your driving style.
2. Cold air (or less warm air is better for engine when compared with hot air)
3. Rather than spending 500 rs (on average) every month on changing the stock air filter, buy this once, and wash it with shampoo every 15 days.. or even 30 days.. and it'll last with you very easily for over a year.
If you want a cheaper option, i am selling a used Cold air intake that can fit your car. Contact me 0333-4421822
link to my add: https://www.pakwheels.com/forums/preventive-maintenance-parts-oils-fluids/165289-cold-air-intake-sale-mushroom#post2779933
(Note: with the fittings, i can also arrange for a brand new cone filter rather than the used mushroom in pics)