i want to buy a video transmitter for a quadcopter which could give me couple of km range.

i see that right now only 5.8ghz systems are available on indian hobby sites and that too 200mw ones. would really appreciate if you guys could provide me with some links. 

I don't know much about fpv but you can choose the one you need from here
http://hobbyking.com/hobbyking/store/__754__540__FPV_Telemetry-900MHz.html

Which FPV is best for beginners even I'm interested in buying a FPV. Please suggest me also some good beginner fpvs.
Hobbyking has range of FPV starting from 900mhz to 5.8ghz
Which one is preferable and y. Can those FPV connect with FPV goggles .??

see thing is that 900mhz is supposed to give more range than 5.8ghz for same amount of power but 900mhz has a lot of interference so your range will get decreased. There 200mw 900mhz transmitters which give only a range of 1km(but are supposed to give a lot more). and there are dragonlink uhf systems which live upto their expectations but are insanely costly. So you really have to read the reviews of system to know how much range you can expect from those systems.