I assume your Vios is totally stock at the moment.

If you want more performance out of your current car, you would need the following:
-better wheels/tires
-better suspension
-better brakes

That is before you go for better power.

What is your budget for your upgrades or performance goals? Do you want to take the car to the chassis' limits or do you want to scare yourself sh*tless?

As for fuel consumption, it takes more fuel to make more horsepower.

For starters, you could probably change the air filter to a less restrictive type and upgrade the muffler to a freeflow type like in the link below:

http://images.minitruckinweb.com/tec...ow_muffler.jpg

If you can't find one, you can have it made for you. The reason is that type would reduce the exhaust backpressure and still retain the exhaust's relatively quiet sound. It also looks less obvious if you like a "sleeper" look.