1. It is not advisable to leave your aquarium lights on at all times for the aquarium. You should keep the lights on for 8-12 hour periods at a time. If you want to keep the tank lights on when you arrive home, simply get a timer for the lights so your fish stay on a schedule.
2. 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.
3. It is generally recommended to use natural gravel for the aquarium. Colored gravel can be used, as long as it is professionally made, certain cheaply made color gravels can be toxic to fish in your aquarium.