First, you'll need a petticoat underneath (you can't wrap a sari without one), and fabric for a blouse. Finer saris come with blouse pieces, so a tailor can continue the sari's border design when he sews the blouse.
If you're shopping for saris in New Delhi, I suggest the Khazana boutiques, with branches at various Taj hotels. The largest and best boutique is on two floors of the Taj Man Singh Hotel. The staff there will take a woman's measurements and sew a blouse in a few days.
Expect to pay over $100 for a good sari (made of substantial weight silk, one of a kind), but less for chiffons or informal designs.
The salwar kameez is another popular outfit for women. The kameez (I hear this is where the French got chemise) is a long tunic-style top, and salwar refers to slim pajama pants underneath.