Minimal Gulp Configuration

gulpfile.js

var gulp = require('gulp');
var sass = require('gulp-sass');
var uglify = require('gulp-uglify');
var concat = require('gulp-concat');
var rename = require('gulp-rename');
var wait = require('gulp-wait');

gulp.task('bundleCSS', function(){
  return gulp.src('./sass/style.scss')
    .pipe(wait(500))
    .pipe(sass(
        {
          'includePaths' : ['./sass/'],
          'outputStyle' : 'compressed'
        }
      )
      .on('error', sass.logError)
    )
    .pipe(rename({suffix: '.min'}))
    .pipe(gulp.dest('./dist'))
});

gulp.task('bundleJS', function() {
  return gulp.src([
      './js/jquery.js', 
      './js/jquery-validation.js',
      './js/slick.js',
      './js/main.js'
    ])
    .pipe(wait(500))
    .pipe(concat('bundle.js'))
    .pipe(rename({suffix: '.min'}))
    .pipe(uglify().on('error', function(uglify) {
      console.error(uglify.message);
      this.emit('end');
    }))
    .pipe(gulp.dest('./dist'));
});

gulp.task('watch', ['bundleCSS','bundleJS'], function (){
  gulp.watch('./sass/**/*.scss', ['bundleCSS']);
  gulp.watch('./js/**/*.js', ['bundleJS']);
});