Module Spacing

.rt-block class used to the space between the modules.

Solution 1: 

First of all, select the field (Position) to use.
For example: Feature Module Position 

You can see my changes below:

You can add this code anywhere: For Example: templates/gantry/css/template.css

#rt-feature .rt-container .rt-block {margin:15px 0 15px 0 !important; padding:0px !important;} /* #rt-feature .rt-container .rt-block {margin:15px !important; padding:10px !important} */


#rt-feature .rt-container .rt-block {margin:0 !important; padding:0px !important;} /* #rt-feature .rt-container .rt-block {margin:15px !important; padding:10px !important} */

Solution 2: 

.rt-block was described here: templates/gantry/less/gantry-core.less (line 31)
Attention please, If you change this, many places are affected. But, If you want, you can try it.

Below, you will find a highlighted answers:

// Blocks                 -> line 30
.rt-block {                 -> line 31
padding: 15px; -> You can change this value: for example: padding: 7px or padding: 10px 0; or padding:0 10px 5px 10px;
margin: 10px;   -> You can change this value: for example: margin: 7px or margin: 10px 0; or margin:0 10px 5px 10px;
position: relative;