No need to bother so much about ISO because that is not the first issue you gonna pay attention on your creation...

First thing is composition. If you found out you're very difficult to stick with rule of third when you're shooting, edit it later on so that the subject is framed nicely. Scenery photo, seriously lack of perspective, lead in line, and foreground interest...

And second is about lighting. A photo shouldn't be overexposed or underexposed unless it's intended to be (for HDR, high contrast BW photo and etc). Both ways will cause data missing and can't be recovered even though gone through PP. My suggestion would be using Aperture Priority mode or Shutter Speed priority mode instead of Manual mode. Let the camera estimate and adjust the exposure for you.

All the best!