How to add space between bitmap of spinner selector and items of drop down list

Try using a layer-list

bg_spinner.xml

<?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
    <item>
        <!-- This is the actual spinner background -->
        <selector >
            <!-- Feel free to use your own drawable for these states -->
            <item android:state_window_focused="false" android:drawable="@drawable/bg_border_accent_thin"/>
            <item android:state_pressed="true" android:drawable="@drawable/bg_border_accent_thin"/>
            <item android:state_window_focused="true" android:state_pressed="false" android:drawable="@drawable/bg_border_grey_thin"/>
        </selector>
    </item>

    <!-- This is the spinner drawable, use your custom drawable aswell. android:right does the magin to separate this drawable from  the spinner content-->
    <item android:drawable="@drawable/ic_ripple_arrow"
            android:gravity="center_vertical|right"
            android:right="16dp"/>
</layer-list>

Edit 02/02/2020

My apologies for a weekend-long lunch.

If you are using the androidx dependencies (which I suggest you do) here's the code that I use to properly add spacing between the text and the selected item in the spinner.

On your layout.xml

<!-- The line I think you need is the one giving padding to the right -->
<androidx.appcompat.widget.AppCompatSpinner
    android:paddingTop="4dp"
    android:paddingBottom="4dp"
    android:paddingRight="36dp" 
    android:background="@drawable/bg_spinner"
    android:popupBackground="@drawable/bg_spinner_popup"/>

The bg_spinner.xml is the one provided a couple of lines above.

And the popup one doesn't really matter, since it gives some directives on how to paint a background, nothing important but here it is either way...

bg_spinner_popup.xml

<?xml version="1.0" encoding="utf-8" ?>
<shape xmlns:android="http://schemas.android.com/apk/res/android
       android:shape="rectangle">
     <corners android:radius="3dp"/>
     <solid android:color ="@android:color/white"/>
     <stroke android:width="5px" android:color="@color/primaryColor"/>
</shape>