gulpfile.js

// Include require nodejs modules
var gulp = require('gulp');
var gutil = require('gulp-util');
var concat = require('gulp-concat');
var less = require('gulp-less');
var compressor = require('gulp-compressor');

// Define paths
var paths = {
  lessFile: 'includes/css/styles.less',
  lessFiles: 'includes/css/*.less',
  cssDir: 'includes/css',
  cssFiles: 'includes/css/*.css',
  minDir: 'includes/min'
};

gulp.task('css', ['less'], function() {
  // Minify and copy all CSS
  return gulp.src(paths.cssFiles)
    .pipe(compressor())
    .pipe(concat('styles.min.css'))
    .on('error', gutil.log)
    .pipe(gulp.dest(paths.minDir));
});

gulp.task('less', function () {
  // Compile less into CSS
  return gulp.src(paths.lessFile)
    .pipe(less())
    .on('error', gutil.log)
    .pipe(gulp.dest(paths.cssDir));
});

// Rerun the task when a file changes
gulp.task('watch', function() {
  gulp.watch(paths.lessFiles, ['css']);
});

// The default task (called when you run `gulp` from cli)
gulp.task('default', ['css']);

This gulpfile.js allows you to compile less into CSS and then minify the CSS. The task "css" minifies the CSS and is dependant on the completion of the "less" task, as specified by the hint telling it that it is dependant on the "less" task:

gulp.task('css', ['less'], function() {

Where the ['less'] is the hint.

Also the:

.on('error', gutil.log)

Causes the watch task to not error out and stop watching if there is an error in the less file(s) you pass into it. Instead the error is output to the console and the tasks continues to watch.

You can take out 'less' on line #36 -- 'css' runs and has a dependency of 'less'. Same for #line 40.

Thanks Todd so it does. Updated as suggested.