gulpfile.js

// Define gulp before we start
var gulp = require('gulp');

// Define Sass and the autoprefixer
var sass = require('gulp-sass');
var prefix = require('gulp-autoprefixer');

// This is an object which defines paths for the styles.
// Can add paths for javascript or images for example
// The folder, files to look for and destination are all required for sass
var paths = {

    styles: {
		src: './app/Admin/assets/sass',
		files: './app/Admin/assets/sass/**/*.scss',
		dest: './public/css/admin'
	}

}

// A display error function, to format and make custom errors more uniform
// Could be combined with gulp-util or npm colors for nicer output
var displayError = function(error) {

    // Initial building up of the error
    var errorString = '[' + error.plugin + ']';
	errorString += ' ' + error.message.replace("\n",''); // Removes new line at the end
    
    // If the error contains the filename or line number add it to the string
	if(error.fileName)
		errorString += ' in ' + error.fileName;

	if(error.lineNumber)
		errorString += ' on line ' + error.lineNumber;

    // This will output an error like the following:
    // [gulp-sass] error message in file_name on line 1
	console.error(errorString);
}

// Setting up the sass task
gulp.task('sass', function (){
    // Taking the path from the above object
	gulp.src(paths.styles.files)
    // Sass options - make the output compressed and add the source map
    // Also pull the include path from the paths object
	.pipe(sass({
		outputStyle: 'compressed',
		sourceComments: 'map',
		includePaths : [paths.styles.src]
	}))
    // If there is an error, don't stop compiling but use the custom displayError function
	.on('error', function(err){
		displayError(err);
	})
    // Pass the compiled sass through the prefixer with defined 
	.pipe(prefix(
		'last 2 version', 'safari 5', 'ie 8', 'ie 9', 'opera 12.1', 'ios 6', 'android 4'
	))
    // Funally put the compiled sass into a css file
	.pipe(gulp.dest(paths.styles.dest))
});

// This is the default task - which is run when `gulp` is run
// The tasks passed in as an array are run before the tasks within the function
gulp.task('default', ['sass'], function() { 
    // Watch the files in the paths object, and when there is a change, fun the functions in the array
	gulp.watch(paths.styles.files, ['sass'])
    // Also when there is a change, display what file was changed, only showing the path after the 'sass folder'
	.on('change', function(evt) {
		console.log(
			'[watcher] File ' + evt.path.replace(/.*(?=sass)/,'') + ' was ' + evt.type + ', compiling...'
		);
	});
});

package.json

{
  "devDependencies": {
    "gulp": "^3.5.5",
    "gulp-sass": "^0.7.1",
    "gulp-autoprefixer": "~0.0.3",
    "gulp-minify-css": "0.1.0",
  }
}