How do I clear the entire system of all my testing data?

Jobs, requests, custom offers and users can be deleted from the admin dashboard.
Go to cPanel/ FTP > File Manager > public_html > create new file (click 'File' link from header) > insert 'clear-wpj-tables.php' > click Create New File.
Right-click on the newly created file > Edit > Edit > Paste the following code and Save.
$scriptPath = dirname( __FILE__ );
$path       = realpath( $scriptPath . '/./' );
$filepath   = explode( "wp-content", $path );

define( 'WP_USE_THEMES', false );
require( '' . $filepath[0] . '/wp-load.php' );

global $wpdb;

$tables = array(

foreach ( $tables as $table ) {
	$wpdb->query( "TRUNCATE TABLE " . $wpdb->prefix . "job_" . $table );

echo 'Your test data has been successfully deleted'; ?>

After that, go to browser url and type YOUR_SITE_URL/clear-wpj-tables.php

Replace YOUR_SITE_URL with the actual URL address of your site.

We strongly recommend to make database backup before you make any changes in database in case of any issues.
If someone wants to keep few users but wants to delete their data stored in usermeta:
You can use plugin and steps mentioned in below link to delete the data related to the users you want to keep.