Свойство grid-gap

grid-gap: grid-row-gap grid-column-gap;

<!DOCTYPE html>
<html lang='ru'>
<head>
<meta charset='UTF-8'>
<meta name='viewport' content='width=device-width, initial-scale=1.0'>
<title>Document</title>
</head>
<body>
<style>
 .grid-container {
 display: grid;
 grid-template-columns: auto auto auto auto;
 grid-gap: 20px 50px;
 background-color: #2196f3;
 padding: 10px;
 }
 
 .grid-container > div {
 background-color: rgba(255, 255, 255, 0.8);
 text-align: center;
 padding: 20px 0;
 color: black;
 font-size: 30px;
 }
 </style>
 
 <div class='grid-container'>
 <div class='item1'>1</div>
 <div class='item2'>2</div>
 <div class='item3'>3</div>
 <div class='item4'>4</div>
 <div class='item5'>5</div>
 <div class='item6'>6</div>
 <div class='item7'>7</div>
 <div class='item8'>8</div>
 <div class='item9'>9</div>
 </div>
</body>
</html>