How to put spacing between TBODY elements

Something like this will work, depending on your browser support requirements:

tbody::before
{
  content: '';
  display: block;
  height: 15px;

}

Try this, if you don't mind not having borders.

<style>
table {
  border-collapse: collapse;
}

table tbody {
  border-top: 15px solid white;
}
</style>

<table>
    <tfoot>
        <tr><td>footer</td></tr>
    </tfoot>
    <tbody>
        <tr><td>Body 1</td></tr>
        <tr><td>Body 1</td></tr>
        <tr><td>Body 1</td></tr>
    </tbody>
    <tbody>
        <tr><td>Body 2</td></tr>
        <tr><td>Body 2</td></tr>
        <tr><td>Body 2</td></tr>
    </tbody>
    <tbody>
        <tr><td>Body 3</td></tr>
        <tr><td>Body 3</td></tr>
        <tr><td>Body 3</td></tr>
    </tbody>
</table>

People will always have controversial opinions about using empty table elements to layout a page (as evidenced by this answer's downvote). I recognize this, but sometimes its easier to use them this way when you are working in a "quick and dirty" way.

I've used empty rows in past projects to space groups of table rows. I assigned the spacer rows a css class of their own and defined a height for that class that acted as a top and bottom margin for that group of table rows.

    .separator{
             height: 50px;
    }

   <table>
           <tr><td>Cell 1</td><td>Cell 2</td></tr>
           <tr><td>Cell 1</td><td>Cell 2</td></tr>
           <tr><td>Cell 1</td><td>Cell 2</td></tr>

           <tr class="separator" colspan="2"></tr>

           <tr><td>Cell 1</td><td>Cell 2</td></tr>
           <tr><td>Cell 1</td><td>Cell 2</td></tr>
           <tr><td>Cell 1</td><td>Cell 2</td></tr>

           <tr class="separator" colspan="2"></tr>

           tr><td>Cell 1</td><td>Cell 2</td></tr>
           <tr><td>Cell 1</td><td>Cell 2</td></tr>
           <tr><td>Cell 1</td><td>Cell 2</td></tr>
   </table>

If you don't have borders on your table cells, you could also define a height to your typical cell or row in your style sheet that evenly spaces out all rows of your table.

tr{
   height: 40px;
}