Hello Ciatronical
For example you should use:
User-agent: * 
Disallow: /system/ 
allow: /system/css 
allow: /system/js 
Disallow: /tmp/
allow: /tmp/*.js
allow: /tmp/*.css
Sitemap: https://_valid_domain.com_/sitemapindex.xml
User-agent: googlebot
Allow: /themes/
Allow: /system/js
Allow: /system/css
Regards, Pavel.