If you're having problems with ISO ..
Buy some sort of tri-pod and use longer shutter speeds and eliminate the need for ISO

But if you don't fancy lugging around a tri-pod try learning about these main settings on a camera.
-Aperture (Size of the camera opening)
-Shutter Speed (How long the shutter is open)
These effect how bright or dim your image is.
ISO changes the sensitivity of the sensor to light, high ISO means it is more sensitive to light so your image is brighter when you're really lacking light. But the price you pay is extra pixels creating 'noise' .. To elminiate the need for high ISO (in low-light conditions)
You need to put your camera on manual and set aperture to F11 <Or higher if you can> and Shutter speed to a good enough time to gather sufficient light.
If you read more about this online I'm sure there is something that is much clearer and more in depth than my quick explanation .. If you're already fiddling with these settings and still having to up ISO then look into saving for the cameras suggested above with more advanced ISO systems.
Again, hope this helped !