WordPress: Loading multiple scripts with enqueue

First thing jquery in there by default in wordpress so you dont have to register it , just enqueue it

most of the jquery ui libs and core jquery files are already registered with wordpress so you only need to enqueue with right handle look here enqueue script

wp_enqueue_script is used to enqueue script and wp_enqueue_style is used to enqueue style

for calling custom js, its better to register script or style first before using

wp_register_script // to register script

wp_register_style // To register style

then enqueue using wp_enqueue_script, wp_enqueue_style

here is a sample code snippet for whole process from my site

function pr_scripts_styles() {

    wp_enqueue_script('jquery'); // just enqueue as its already registered 
    if ( is_singular() && comments_open() && get_option( 'thread_comments' ) )
        wp_enqueue_script( 'comment-reply' );

    /*   REGISTER ALL JS FOR SITE */
    wp_register_script('pr_cycle_all',get_stylesheet_directory_uri().'/js/pr-slider.js');
    wp_register_script('pr_slider',get_stylesheet_directory_uri().'/js/jquery.cycle.all.min.js');
    wp_register_script('pr_validation_engine',get_stylesheet_directory_uri().'/js/jquery.validationEngine-en.js');
    wp_register_script('pr_validation_locale',get_stylesheet_directory_uri().'/js/jquery.validationEngine.js');
    wp_register_script('stylethemes',get_stylesheet_directory_uri().'/js/stylethemes.js');
    wp_register_script('pr-jquery-ui',get_stylesheet_directory_uri().'/js/jquery-ui.js');
    wp_register_script('main-js',get_stylesheet_directory_uri().'/js/main.js');
    wp_register_script('pr-galleriffic',get_stylesheet_directory_uri().'/js/jquery.galleriffic.js');
    wp_register_script('pr-rollover',get_stylesheet_directory_uri().'/js/jquery.opacityrollover.js');
    wp_register_script('pr_colorbox',get_stylesheet_directory_uri().'/js/jquery.colorbox.js');
    wp_register_script('pr_jcarousel_js',get_stylesheet_directory_uri().'/js/jquery.jcarousel.min.js');


    //wp_register_script('google-map-api','https://maps.googleapis.com/maps/api/js?v=3.exp&sensor=false');



    /*   REGISTER ALL CSS FOR SITE */
    wp_register_style('pr_woocommerce',get_stylesheet_directory_uri().'/css/_woocommerce.css');
    wp_register_style('pr_mobile',get_stylesheet_directory_uri().'/css/mobile.css');
    wp_register_style('pr_sec_teal_grey',get_stylesheet_directory_uri().'/css/secondary-teal-grey.css');
    wp_register_style('pr_site_options',get_stylesheet_directory_uri().'/css/site-options.css');
    wp_register_style('pr_teal_grey',get_stylesheet_directory_uri().'/css/teal-grey.css');
    wp_register_style('validation_css',get_stylesheet_directory_uri().'/css/validationEngine.jquery.css');
    wp_register_style('galleriffic_css',get_stylesheet_directory_uri().'/css/galleriffic.css');
    wp_register_style('pr_colorbox_style',get_stylesheet_directory_uri().'/css/colorbox.css');
    wp_register_style('pr_jcarousel_css',get_stylesheet_directory_uri().'/css/jcarouselskin.css');



    /*   CALL ALL CSS AND SCRIPTS FOR SITE */
    wp_enqueue_script('pr-jquery-ui');
    wp_enqueue_script('stylethemes');

    wp_enqueue_script('pr_cycle_all');

    wp_enqueue_script('pr_slider','','','',true);
    wp_enqueue_script('pr_validation_engine');
    wp_enqueue_script('pr_validation_locale');
    wp_enqueue_script('google-map-api');
    wp_enqueue_script('main-js');
    wp_enqueue_script('pr-galleriffic');
    wp_enqueue_script('pr-rollover');
    wp_enqueue_script('pr_colorbox');


    wp_enqueue_style( 'pr-style', get_stylesheet_uri(), array(), '2013-07-18' );
    wp_enqueue_style('pr_site_options');
    wp_enqueue_style('pr_woocommerce');
    wp_enqueue_style('pr_mobile');
    wp_enqueue_style('pr_sec_teal_grey');
    wp_enqueue_style('pr_teal_grey');
    wp_enqueue_style('validation_css');
    wp_enqueue_style('galleriffic_css');
    wp_enqueue_style('pr_colorbox_style');
    if(is_single()){
        wp_enqueue_script('pr_jcarousel_js');
        wp_enqueue_style('pr_jcarousel_css');
    }
}
add_action( 'wp_enqueue_scripts', 'pr_scripts_styles' );

also remember to hook your function with wp_enqueue_scripts so that scripts & style load correctly add_action( 'wp_enqueue_scripts', 'pr_scripts_styles' );