Quote: Also, i havent got any filters yet , suggest me an economical one.
You're not going to like the answer, but do not go for "economical" if that means "cheap".
*anything* you put in front of your lens is going to degrade the image.
A good filter will do so as well, but with the least visible effect.
I would also not suggest going right out and buying a $300 filter!!
They are better than the $10, but not *that* much.
My first suggestion would be a polarizer. It will help cut the light as well as reduce reflections and boost saturation and contrast -- as a result of reducing the reflections on many materials such as leaves, etc...)
Linear polarizers are cheaper and work just as well as circular. There is a HUGE MYTH about linear polarizers affecting metering and/or focus, but I have yet to see any proof of that (and I have tested both).
Sadly, linear have fallen behind in tech due to scare tactics causing people to avoid them, so you may be stuck with circular to get one with good coating to eliminate flare.
Buy one big enough to fit your largest lens, and buy step-down rings to fit your other lenses. (a $10 ring is a lot cheaper than another polarizer, and a lot easier to carry and care for.) Polarizers tend to be a bit expensive, and I don't see the need to have more than one.
If you're doing lots of landscapes, you might want an ND-grad filter (neutral density graduated).
It will be dark on one end and gradually become clear at the other.
This will allow you, for example, to darken down the skies while allowing the ground to remain unaffected.
i.e. It helps balance out both to be within the limits of what your camera can handle.
FYI
I would not spend more than $75-100 on a polarizer (and a lot less for a ND).
I think the biggest mistake I feel I have ever made was being tricked into buying a $250 circular polarizer. It rarely gives any different results than the $50 filter I had used for many years!!)
The debatable portion of this is that you should spend the most money you can afford on your lens, and on filters.
If you had unlimited funds, buy the best gear you can find.
Sadly, the world isn't perfect so you'll need to balance your income with your perceived need for perfection and your skill level.
For my first five years I could not see how poor my $50 lens and $5 filter was... I loved what I took photos of and I had a blast.
Now I look back at those and chuckle at the low quality. I'm not sure if a $1400 lens would have been wasted on me at the time. Maybe I would have improved faster? Or maybe when I dropped that first lens, I would have given up photography because I could never have afforded to replace it.
Anyway, I rambled enough. Hopefully it helped a little bit...
No simple answer.
Any answer (i.e. opinion) can often be debated for days.