I wouldn't get a used aquarium. One can never really know just how it was treated when active and how it was stored when not. I did that and it leaked within 6 months. I'm currently in planning stage with mine, and have researched the equipment I will need and what it will cost me to achieve the goals I have. That way, there are no surprises. That will, at the very least, remove the anxiety of the unknown. The first question to yourself is what are your goals and what you need to achieve them. From there, it's all about studying EVERYTHING. For me, it took months to reacquainte myself with the hobby and answer the goal question, So Greetings! And Welcome to our collective obsession!