The true ISO (unity gain) of the T3/1100D is between 300 and 400, so I wouldn't go lower than 400 regardless, and it's then just a case of exposing sufficiently...that means, with the histogram away from the left edge and with no accumulation of pixels at the right hand edge, therefore clipping neither blacks or whites respectively.
The gain behaviour of this camera is non-linear with ISO however. If you double the ISO to 800, the noise only increases by about 30%. Double it again to 1600 and again doesn't increase by as much as it should. If you're imaging in cool conditions, with ambient temperatures around or below 5C, try taking some darks at ISO1600 and see how they look
