<form action="{get_permalink()}" id="app" method="post">

          <p class="name">
              <input name="name" type="text" class="validate[required,custom[onlyLetter],length[0,100]] feedback-input" placeholder="Your Name" id="name">
          </p>
          <p class="email">
              <input name="email" type="text" class="validate[required,custom[email]] feedback-input" id="email" placeholder="Your Email">
          </p>
          <p class="investment">
              <input name="investment" type="text" class="validate[required,custom[integer]] feedback-input" id="investment" placeholder="Your Investment ID">
          </p>
          <h2 class="file-header">Files Upload</h2>
          <p class="files">
              <span class="file-label">File [1]</span>
              <input name="file1" type="file" class="files-upload" id="file1">
          </p>
          <p class="files">
              <span class="file-label">File [2]</span>
              <input name="file2" type="file" class="files-upload" id="file2">
          </p>
          <p class="files">
              <span class="file-label">File [3]</span>
              <input name="file3" type="file" class="files-upload" id="file3">
          </p>
          <p class="files">
              <span class="file-label">File [4]</span>
              <input name="file4" type="file" class="files-upload" id="file4">
          </p>
          <div class="submit">
              <button type="submit" id="button-blue" name="">Submit</button>
              <div class="ease">
              </div>
          </div>
          <input type="hidden" name="application_form_submitted" value="1">
      </div>

(function($){
    $('#button-blue').click(function(e){
     e.preventDefault();
     var m_data = new FormData();
     m_data.append( 'name', $('input[name=name]').val());
     m_data.append( 'email', $('input[name=email]').val());
     m_data.append( 'investment', $('input[name=investment]').val());
     m_data.append( 'file1', $('input[name=file1]')[0].files[0]);
     m_data.append( 'file2', $('input[name=file2]')[0].files[0]);
     m_data.append( 'file3', $('input[name=file3]')[0].files[0]);
     m_data.append( 'file4', $('input[name=file4]')[0].files[0]);

  $.ajax({
      url: $('#app').attr('action'),
      data: m_data,
      processData: false,
      contentType: false,
      type: 'POST',
      dataType:'json',
      success: function (d) {
           var d = JSON.parse(d);
           alert(d.text);
           },
      error: function (xhr, textStatus, error) {
           alert(error);

       }
       });
  });
  })( jQuery );