There are many things to consider before you buy anything for an aquarium. One of the most important is whether an aquarium is even right for you. Ideally every aquarium receives a water change of at least 25% every week. Once each month the filter needs to be cleaned. Aquariums can be a significant investment so it is important to plan a budget from the beginning and plan accordingly. It is also a good idea to decide what kind of fish you would like to have. Many require large aquariums, wider aquariums, etc. so purchasing an aquarium without taking this into account can cause problems for your fish or require you to choose other types.
I suggest deciding where you are going to put the aquarium. Measure out the largest tank the area will fit. When you go to the aquarium store have the maximum space you can fit the aquarium and a budget. You will need find the largest aquarium that will fit the space and your budget. Make sure you include all equipment in your budget. If you overlook certain pieces of equipment or plan on buying a filter that cannot actually handle the aquarium you will have surprise expenses down the road.
Do not buy anything the first visit to the store. Write down everything you want to buy and then take that to a forum so that more experienced aquarists can give you input.
If pricing becomes an issue I suggest asking the store if they can match online pricing. They will either be thankful you gave them the opportunity to compete and let you know what they can do (even if they can’t quite match the price) or they will say they don’t match online pricing because it is almost impossible to do sometimes and online competition is putting many small businesses out of business, making it a sore spot for them (which you can’t blame them for).
Now is the time to decide what kind of setup you want. Do you want a metal stand or a wood cabinet? Do you want a filter that hangs on the back of the aquarium or a canister that sits underneath the tank inside the cabinet? These are things that can make a huge difference long term but if rushed may not
I suggest a wood cabinet. They look better and provide a great place to hide and store equipment. The reason I would use a metal stand is if I planned on having a second tank on the bottom level. If you decide to do this, or at least have the option, make sure the metal stand you choose allows for this because not all of them do. In addition, I would give the stand a few more coats of a high quality paint, or at least check its paint job. I have seen some metal stands start to rust because the original paint job just wasn’t quite enough to last as long as the aquarium (which can be well over a decade).
Wood cabinets can vary greatly in price and quality. Be aware that many simply use laminated playwood. Any scratches or scrapes to the laminate or even normal wear and tear on the corners can allow water in to the plywood and significantly reduce its strength.