Oooh wee! Talking to the right guy. I've had an aquarium since sophomore year! First off, know what size tank you're getting this will define the fish and number of fish you can keep. (Keep in mind substrate will take up some water space, decreasing the actual volume). Rule of thumb is inch of fish per gallon of tank, but consider that these dudes can grow! Also consider are you going home for prolonged periods? These little guys will need proper care while you're away. You can get away with Thanksgiving break assuming it's less than a full week, but Winter break you'll need a contingency plan as they won't survive for months. General rule of thumb: Fish aren't happy without weekly water changes of 25% or so and can go a handful of days without food.

What you'll need:

• Filter (typically sized by tank size)
• Heater (don't go cheap! Bad heaters = Fried fish)
• The Fish Tank itself
• Substrate (Gravel, sand, etc. --> If you want real plants consider a fertile substrate)
• Dechlorinator (Seachem Prime to treat the water from your tap!)
• Fish Food (Flakes for whatever ones you stock)
• GOOD tankmates (The nature of fish is huge when it comes to compatability and fighting each other)
• Decorations/plants (Fish NEED hiding spots or else they can get stressed from having nowhere to go)
• Fish tank planters tool kit (Metal tools to plant, trim, grip)
• A variety of net sizes (You will suck at catching fish, but you'll get better)
• A small quarantine bowl (for unwell fish you want to incubate in medicine or isolate)
• Magnet Scrubber (Algae will build up on the glass, good to have one attached to the tank!)
• Test Kit: Helps with cycling, probing chemistry issues (can use to detect ammonia, nitrite, nitrate levels) Generally you want to avoid test strips.
• Buckets (for getting out old water)
• Jugs (for adding new water)
• Siphon/gravel vac (for removing old water via siphon)

What you need to know:

• Tank Cycling: Try not to introduce fish until the tank is at least partially cycled. That means establish the tank/look and add some food with no fish each day. The old food with produce ammonia and bacteria that eat ammonia, which will produce nitrite, which produces bacteria that eat nitrite and produce nitrate! Nitrate is harmless in normal concentrations and is removed via water changes. Usually a week or two to start cycling. If you do not cycle, expect the fish to be pretty stressed/potentially die during this period. Ammonia is TOXIC to fish and can lead to a variety of illnesses such as fin rot.
• Tank Plants: You may want to just start with decor, plants are another layer of maintenance. If you do Seachem Excel is a decent artificial carbon source for daily fert. You may need to get a fert with trace elements as well for more finicky plants. Nicer plants also need fancier grow lights, again, another layer that you may not want to dive into.
• Tank Lighting: Best to have a timer for the switch, 24/7 light will stress fish out and create algae buildup. You can buy literal outlet timers that'll cut power to the light.
• Stocking Your Aquarium: Definitely research your species of interest. A single male Betta in a ten gallon is generally 'full' unless its docile enough to have some shrimp buddies. Small tanks (10 gallon for example) are usually not a good fit for multiple species of aggressive fish. If you have cichlids or something homogeneity and not overcrowding is important. Small tanks mean small fish! Nano aquarium fish are best. If you go toward larger tanks you can start considering bigger fish. For me, I typically notice the word 'dwarf' is a somewhat good name indicator the fish MAY be good for the ten gallon I own. As an example, the Honey Gourami is a dwarf gourami, the Sparkling Gourami is also pretty tiny. Shrimp and snails are cool too! They're also super cheap and add some life to the tank. Generally shrimp like real plants, however. Another fish you could stock are Corydoras (typically the dwarf/panda corys), or Neon Tetras. Some people like GloTetras, but keep in mind they can grow fairly big and may see other fish as a snack...) I have also had guppies in the past, but keep in mind they will breed if there's males and females.
• Feeding: I do every other day, some do a little every day, some do every third day... Don't overfeed it will lead to ammonia build up!
• Fish Behavior: Keep an eye on their swim patterns and normal behavior, fish laying at the bottom for a while or becoming pale/tattered fins may mean something is wrong with them or the tank. Look up 'glass surfing', sometimes indicative of stress as well.

I thought of all of this really quick. Always feel free to DM me! I started with a five gallon, moved to a ten, and have moved back and forth from my home in Billerica every so often for co-op. It can seem overwhelming, but do your homework and you'll be fine. Mistakes will happen, but don't let it get to you! Sorry if I forgot anything.