I would say "Good luck ON your journey" could also say "Good luck ON your test " with regards to "to" , i would say : "Good luck TO you!"

Examples: Good luck to you on your marriage with Paul! Good luck on your job search! Wishing ‘good luck’ on a journey suggests that there is some kind of goal. We’d just say Have fun on your trip! Good luck on your trip to Europe! I hope you make some sales. Good luck on your trip to meet the woman you’ve been emailing with!