I don't see how that's supposed to work. You can't just change an array key, it will be ignored by elgg_get_river(), because such key is not supported.
You need to add a custom join and where clauses, because by default the function generates AND statements, you need OR.

Yeah you are right I have no idea what I'm doing. Where are the other array keys supported?

Inline docs are pretty thorough

How much do you think it would cost me to have someone customize my river to include both mine and friends? Maybe I should take this thread to professional services?

I'm kinda lost any help out there? Would this be a big or small job?

$user = elgg_get_logged_in_user_entity();
$dbprefix = elgg_get_config('dbprefix');
echo elgg_list_river([
   'wheres' => [
      "
      rv.subject_guid = $user->guid 
      OR 
      rv.subject_guid IN (
         SELECT guid_two FROM {$dbprefix}entity_relationships
         WHERE relationship = 'friend'
         AND guid_one = $user->guid
      )"
   ],
]);

@Ismayil thanks for posting the query. I also tried to come up with a solution but got stuck (not even close to the solution to be honest).

@Ismayil Khayredinov Seriously thank you so much! that worked perfectly! 

@Ismayil Khayredinov I may have spoke too soon. Now I'm having styling issues. I think its because I'm calling the echo inside of a page_filter. Here's the whole page. Also, how much would you charge to help me with this issue?  Are you on UpWork?

<?php
/**
 * Main activity stream list page
 */

$options = array();

$page_type = preg_replace('[\W]', '', get_input('page_type', 'all'));
$type = preg_replace('[\W]', '', get_input('type', 'all'));
$subtype = preg_replace('[\W]', '', get_input('subtype', ''));
if ($subtype) {
    $selector = "type=$type&subtype=$subtype";
} else {
    $selector = "type=$type";
}

if ($type != 'all') {
    $options['type'] = $type;
    if ($subtype) {
        $options['subtype'] = $subtype;
    }
}

switch ($page_type) {
    case 'mine':
        $title = elgg_echo('river:mine');
        $page_filter = 'mine';
        $options['subject_guid'] = elgg_get_logged_in_user_guid();
        break;
    case 'friends':
        $title = elgg_echo('river:friends');
        $page_filter = 'friends';
        $options['relationship_guid'] = elgg_get_logged_in_user_guid();
        $options['relationship'] = 'friend';
        break;
    case 'combined':
        $title = elgg_echo('river:mine');
        $page_filter = 'combined';
        $user = elgg_get_logged_in_user_entity();
        $dbprefix = elgg_get_config('dbprefix');
        echo elgg_list_river([
            'wheres' => [
                "
                rv.subject_guid = $user->guid 
                OR 
                rv.subject_guid IN (
                SELECT guid_two FROM {$dbprefix}entity_relationships
                WHERE relationship = 'friend'
                AND guid_one = $user->guid
                )"
            ],
        ]);
        break;
    default:    
        $title = elgg_echo('river:all');
        $page_filter = 'all';
        break;
}

$options['count'] = true;
$count = elgg_get_river($options);
$options['count'] = false;

$options['pagination'] = false;
$options['offset'] = 0;
if(elgg_get_config('default_limit'))
    $options['limit'] = elgg_get_config('default_limit');
else
    $options['limit'] = 5;

$script_text = '<script type="text/javascript"> 
        var options = ' . json_encode($options) . '; 
        var numactivities = ' . $count . '; 
        </script>';

$activity = '<div id="river_auto_update_activity">';
$activity .= elgg_list_river($options);
if (!$activity) {
    $activity = elgg_echo('river:none');
}
$activity .= '</div>';
if ($count > $options['limit']) {
    // show load more button
    $activity .= '<center id="river_auto_update_load_more_button"><button style="padding:0 50px;" onClick="loadMore()">Load More</button></center>';
    
    $script_text .= '<script type="text/javascript"> var istheremore = true; </script>';
} else {
    $script_text .= '<script type="text/javascript"> var istheremore = false; </script>';
}
// show the loading gif
$activity .= '<img id="river_auto_update_loading" src="' . elgg_get_site_url() . '/mod/time_theme/graphics/loading.gif" height="25px;" style="display:none; margin-left:auto; margin-right:auto;">';

$content = elgg_view('core/river/filter', array('selector' => $selector));

$sidebar = elgg_view('core/river/sidebar');

$script_text .= '<script type="text/javascript">

 $(window).scroll(function() {   
   if($(window).scrollTop() + $(window).height() == $(document).height()) {            
        loadMore();        
   }
});

</script>';

$params = array(
    'title' => $title,
    'content' =>  $content . $activity . $script_text,
    'sidebar' => $sidebar,
    'filter_context' => $page_filter,
    'class' => 'elgg-river-layout',
);

$body = elgg_view_layout('content', $params);

echo elgg_view_page($title, $body);

?>

@Ismayil Khayredinov, I am using another code to extract only the "Group" activity. How can I club my code with yours so that I can have "Mine"+"Friends"+"Groups Activity" in one go.

My Code:

$db_prefix = elgg_get_config('dbprefix');
$user = elgg_get_logged_in_user_entity();

$groups = $user->getGroups('', false);
$group_guids = array();
foreach ($groups as $group) {
 $group_guids[] = $group->getGUID();
}
$guids_in = implode(',', array_unique(array_filter($group_guids)));

echo elgg_list_river(array(
    'pagination' => true,
    'joins' => array("JOIN {$db_prefix}entities e ON e.guid = rv.object_guid"),
    'wheres' => array("e.container_guid IN({$guids_in})"),
    'order_by' => 'e.time_created desc'
 ));