1. Only use medication in your aquarium when you are out of other options. You should use a separate tank to medicate sick fish as some medications can have harmful effects on healthy fish.
2. It is good to budget out the cost of your aquarium. You should leave plenty of money to purchase quality filters, pumps, and heaters for your aquarium. Your big aquarium is going to do you no good if you do not have the proper equipment to keep it going.
3. When you purchase your aquarium and the equipment for your setup, do not purchase the fish at the same time. You are going to need plenty of time to cycle the water in the aquarium to make it hospitable for the fish in your aquarium.