Light meter of any kind won't change your picture. Based on where it is placed and where it is pointing to, it will suggest what shutter speed/aperture to use. It will require interpretation of a figure that it will give you. All it does is measure light based on a standard.

Your camera can do the same thing, IF you know how to use it.

Is correct exposure one of your problems? Matrix metering on these cameras do pretty well unless you are working with tricky situations - in which case, you can switch to spot metering.

If you are going to get a light meter, I'd suggest little more advanced model, like 308 or higher.