What we did last year, built a new house, cemented the floor and aligned it. Walls have been plastered, the only room we use has not been painted yet but Sufeedi(Some white stuff) has been applied, 1 bathroom has been made properly, haven't gone for Tile/Marble yet, only carpet in 1 room and the rest is Kacha but liveable.
Total cost was about 20 lacs. I am sure it would be higher in Islamabad and these rates are for 2012. Ceiling hasn't been done, did RB Lantern(Sariya+Bricks). Foundations are I think 8ft deep.
My opinion: Just do the front portion now so you can easily shift in it and live. The rest can be done after 1-2 years or when Allah SWT allows. So, Garage- No need for fancy tiles etc. Just Plastered walls/floor. Lounge/sitting room+ Kitchen will be used everyday, so it is worth spending some money on it. Same goes for Bedroom and 1/2 Bathrooms.
Sorry for low quality replies, never understood construction biz 