pumping ISO no good D:<
Good to get a SB-600/or any hotshoe flash, as it's really fun to play with flash and to learn them.
with a usual 5-room HDB flat, just do bounce flash.
Bouncing flash is simple, EG. if you are shooting landscape, point your flash upwards to shoot on the ceiling for the flash to bounce OFF the ceiling to make the light less harsh (by alot) and making the effect rather nice.
Also, if shooting portrait, point your flash upwards too and bounce flash onto the ceiling.
Bounce flash is always a good thing, never a good thing to direct blast on the subject, might blind the person, and the effect would be (N).