If you decided to build a house, wouldn't the first thing to do be to decide on what kind of house, where, with how many bedrooms? That is where you are with an aquarium too. What kind of aquarium are you going to set up? It could be a minimum maintenance, low light tank. Or, it could be a high light, pressurized CO2, planted with high light demnding plants. Or, it could be something in the middle, say a moderate light tank, with slow growing plants. All of this to say, first decide on what kind of aquarium you want, how much maintenance you are willing to do, and what types of plants you are interested in. Then, you can start making the other decisions about light, fertilizing, CO2 method, etc.