Zac,
Before you spend money on supplements, I would look at your meal plan first. While I know it is hard to eat on a student's schedule, you don't need to eat 6-8 times a day to build a solid physique. 3 times a day with some supplements and/or healthy snacks is fine. The key is to eat enought of your macronutrients in the time you have to eat.
First off, protein will be your #1 priority to fuel growth. Second will be carbs and healthy fats. Use Scott's Meal Plan tab on the home page to calculate what you minimally need each day. Don't worry about your metabolism or your weight. You are still young and won't completely finish growing until your early 20's so you have plenty of time to put on quality weight and size. It is better to have quality muscle gains and average weight gain than massive weight gain with muscle and fat. Chicken, beef, fish, and eggs are all available in Australia and relatively cheap (I live in Singapore and most of our meats come from Australia). Oats, rice, and whole grains (pasta, etc) are readily available as are plenty of fresh fruits and vegetables. If you have a big bowl of oatmeal with eggs and fruit in the morning, some meat/grains/veggies for lunch, and meat/fish and grains and veggies for dinner, you should have enough macros to fuel and support your growth - and that is just eating 3 times a day. Healthy snacks are nuts (walnuts, almonds), fruits, or greek yogurt.
As for supplements, I would just get a good whey or egg protein and a good casein (milk) protein powder. Whey/egg after workouts or with meals and milk protein with water right before bed. Casein is a mixed bag. I personally am not a fan and it only provides temporary gains in size and strength which you lose once you stop. It also stresses your kidneys and requires you to drink lots of water to stay hydrated. Not worth it in my opinion.
If you do your best to eat 3 times daily as described above, add in some protein supplementation, train smart and get enough sleep, the growth and strength will come in time.
John