Как сделать отступы элементам в JavaScript

А зачем стили добавлять с помощью JavaScript?

<script>
	$('.direction-blocks').slick({
		arrows: false,
		dots: true,
		dotsClass: "my-dots",
  infinite: true,
  speed: 800,
  slidesToShow: 3,
  slidesToScroll: 1,
  autoplay: true,
  autoplaySpeed: 8000,
  responsive: [
    {
      breakpoint: 1024,
      settings: {
        slidesToShow: 3,
        slidesToScroll: 3,
        infinite: true,
        dots: true
      }
    },
    {
      breakpoint: 600,
      settings: {
        slidesToShow: 2,
        slidesToScroll: 2
      }
    },
    {
      breakpoint: 480,
      settings: {
        slidesToShow: 1,
        slidesToScroll: 1
      }
    }
    // You can unslick at a given breakpoint now by adding:
    // settings: "unslick"
    // instead of a settings object
  ]
		});
$('.slick-slide').css({
  "margin-left": "+=10",
  "margin-right":"+=10"
});
	</script>