When looking for a tank, there are many things to consider. To start off the larger the tank, the more fish you can have, this can also mean the more types of fish you can have. When purchasing a tank, you can go anywhere you trust. Many people can find deals on Craigslist you could also try r/Aquaswap on reddit (http://www.reddit.com/r/AquaSwap/). Once you have your tank make sure you test it out to make sure it won’t leak (do this outside of your house so you don’t ruin your floors). The easier tanks for beginners range from 15 to 55 gallons so those will be focused on (keep in mind most fish like to swim side to side or laterally/horizontally, not vertically so a longer tank is generally better than a tall hexagonal one. Also a long one is easier to clean.) . You will need a stand for your aquarium, for viewing ease as well as cleaning ease. Make sure the stand can support the weight of the aquarium. Water weighs around 8 pounds a gallon and you will have a lot of gravel in the tank as well.