Ok, 450mm is a good size to start with since electronics for it are easily available.
Will recommend that you stick with the most common specs. which willl be low cost as well.
Battery: 3 Cell LiPo
Motor (KV): 900KV to 1200 KV
Prop: 10 to 8inch prop

Remember,
Higher KV Motor + small prop = Agile quad + less efficiency.
Lower KV motor + Larger prop = Stable Quad + More efficiency (Mostly used)

well...that was helpful (though i know a bit of it)...any idea on which brands to go for?
wanna make it as cheap as possible

Well, the answer is simple.
If you need it cheap, instead of thinking of brands, just choose the one you find cheapest

i mean hk stuff... they have hundreds of them for same price

got the motors..1000kv...9 inch prop...20 amp escs will work fine na?
what abt controller?

A 10 inch prop will be better than a 9 inch since it will be more stable.
Make sure that the motor can take on a 10 inch prop though.
It should.

Also check if the 20A ESC is enough with 10 inch props.
You should select an ESC with atleast 10% higher Amp Rating that the max Amp rating of the motor.

As far as FCB goes, nothing beats a KK2.1 for beginners.
Out of stock at HK, but in stock at Quadkopters.com

how about kk 5.5? i getting that for 1k...2nd hand

KK5.5 or any similar boards are good if you like headaches.
Configuring them gets heavily messy at times.

I personally never recommend anything similar to a KK5.5 to a beginner.
But since you're on a uber low budget, i guess we are out of options.

budget not an big issue....spending 10k on electronics doesn't make me stingy for another 1k

Then get a KK2.1
It will make the configuration part much easier.

And the bonus is that there are tons of videos available on the web for KK2.0/2.1
And you won't even need the USBASP upfront.

how about apm 2.52
a bit costly but then its arduino compatible...and comes with gps interface

http://www.quadkopters.com/product/apm-2-52/

does this require anything else for gps modulation?

Configuration on APM too can get messy because of enormous features.
Also, with APM, you do also need the power module which is not cheap. You can use a BEC but that will further make things more and more complicated.

You won't be happy crashing a quad with an expensive board like APM.
Configure with KK2.1, learn flying, practise more and then upgrade to APM and do autonomous flights.

http://www.quadkopters.com/product/221213-1000kv-brushless-outrunner-motor-with-mount/

using these motors...description says max current =4-10amp.. >75% throttle

so 20 amp should work fine with 10 prop right?

yep, should be fine.

do we get a cable with programmer boards? and what if it comes with an lcd? can we still connected with lappy? what softwares for calibration? any thread or video to learn that?
plz excuse my stupid question...i'm a totally newbie to multirotors

got 4X1000 kv motors... but i've been strictly advised not to use 10'' props. as some people previously burnt their motors... whats your opinion?
will it be a problem if i'm using 30 amp esc?
what thrust will i get if i'm going for 20 amp esc and 9" prop?

Let me guess...
Maybe they were using higher pitch props?

10X4.5 or 10x4.7 props should be fine with 1000KV.
Do you have people complaining with 10x4.5 on the same motor?

Do one thing, Start with a 10x4.5 prop. If you don't find the motor to be too hot after flight, then no need to change it.
If the motor is too hot then only change to a 9X4.7 prop.

Any 15+ Amp ESC will be fine.

There won't be any thrust different no matter if you use 15A or 20A or 30A or even 100A ESC.
Please spend some time on YouTube.

Check with the store where you got it from for thrust data for different props.
And please stop using inch only for describing a props. Pitch do plays a major role as well.

You usually don't get the UBSASP along with FCB's but a LHS might bundle and sell it along.

On a non-LCD Board
You need the cable for Firmware updates as well as changing major configurations (like setting the mode X or +).

With a LCD Board (KK2.0/2.1)
You need the cable only for Firmware updates. Any and all configuration can be done right from the on board LCD itself.

Stay away from Firmware updates for first 50 hours or so. It can get messy at times.

Lots of threads and videos available with a common friend of ours.
They call it Google

haha ohk..can u calculate the thrust of a 1000 kv motor with 20amp esc and 9X4.5 prop?
and send me a link to how to calculate it
ty

hey there, i've got motors, kk2.1, and props...all i need is esc... will normal hobbyking 18amp good enough? people suggest to use costly turnigy plush 25amp

Hobbysea.com gives hobby king escs at 650... Will they work fine with quad?
http://hobbysea.com/products.php?25&cPath=15

waiting for your quick reply, on the verge of finishing my quad... just left with esc's

and how is it different from
http://hobbysea.com/products.php?353&cPath=15
and
http://hobbysea.com/products.php?246&cPath=15

i want my first quad to function well

my quad done... not able to set kk2.1 ... please help

Not sure why props are on if the configuration part is still not complete.
If you don't want to hurt yourself then take my advice. Put the quad aside for 1-2 days and spend as much time as possible on YouTube learning about KK2.0/2.1 and it's configuration.
Then remove the props and carry out the configuration as per the videos.

Once you are 100% sure that you have configured the quad correctly, then and only then put on the prop and then go outside on a calm non-windy day and try the first spool up.