Santosh, there are way too many variables to know how to answer your question. Where will you work and what is your tolerance for living somewhere else? Will your spouse/partner be working or at home? Will that influence location? Do you like urban living or prefer something green? Hong Kong is extremely convenient in terms of transportation, so you have a lot of options.
For myself, I chose to live on Kowloon side equidistant from my too offices and boss in Central. That puts me in Mongkok (actually Prince Edward) which many expats can't seem to get over...but I love it. Old building with no services, the trade-off is a high ceiling, nicely finished flat with light and spaciousness that is very hard to find here. I pay twice what I would in Tseung Kwan O at the eastern extreme of the greeen MTR line. Some say I pay too much ;-) but I like my landlord and vice versa--so am content (at least until my next of three pay cuts!).
Rent is the biggest cost - be prepared to pay 2 months deposit plus your first month on signing a lease for two years - make sure to get a break clause.
I run at about 600/month for my Octopus card (transportation). Food all depends on how you like to eat, in or out, etc. You can get but with a few hundred in a month....or blow a thousand in one dinner.
Good luck - and welcome ;-)
J