Hi and welcome to the forum
If you visit a few pet shops and look at their aquariums and fish, then write the fish names down and the details of the tanks and post them on here. Then we can give you more info on what can be kept in that tank.
Basically there are lots of different size aquariums and you want to go as big as possible with what you can afford. The bigger the aquarium the more water it holds, and more water means the water chemistry will be more stabile and you will be able to keep more fish and a wider variety of fish. So if you can check out some tanks online or at pet shops and then post the info on here we can discuss them further.
A few basic items that you will need include:
Aquarium
Polystyrene foam to go under the tank and cushion the base of it
Coverglass to reduce evaporation and stop fish jumping out. (not essential but is helpful)
Filter
Substrate (gravel or sand)
Heater if you want tropical fish.
Light if you want to grow aquatic plants or view the fish after dark
Basic test kit that tests water for ammonia, nitrite, nitrate & pH. And if you want to go a bit further you can get a test kit for general hardness (GH) and carbonate hardness (KH). GH & KH test kits are not necessary unless you are trying to keep wild caught fish, and most pet shops will do water testing for you. So if you just want to get it checked every now and then, you can take a glass full of tap water or tank water to the pet shop and get them to test it for you. Some shops will do free water testing while others charge a small fee.
Water conditioner to remove chlorine/ chloramine from tap water
A picture or some coloured card to go on the outside of the back of the tank. The picture makes the fish feel more secure and generally makes the tank look better.
A couple of clean buckets used purely for the fish
A basic model gravel cleaner like the one in the following link.
https://www.about-goldfish.com/aquarium-cleaning.html
All fish are the same to keep, the only difference is tropical vs cold water and fresh water vs salt water. Freshwater tropical fishes are the most commonly kept and pretty easy to keep as long as you do regular partial water changes and don't feed too much.
Normally you get the tank and equipment home, rinse the tank out with fresh water (do not use soaps or cleaning products) and put it on the polystyrene on the stand.
Rinse the gravel/ sand out in a bucket of water until it comes out clean and then add the substrate to the tank. The best way to wash the gravel is to add a couple of inches of gravel to a 10 litre bucket, then hose it a bit, tip the water out, hose it again, tip the water out, and so on until the water is clean. Then add that gravel to the tank and put some more gravel into the bucket to clean.
Once the gravel is in the tank fill the aquarium up about 3/4 with tap water and add some water conditioner to remove the chlorine/ chloramine.
Depending on the type of filter you get will determine if you install the filter before adding the gravel, or after. If you use an undergravel filter, they have plastic plates that go underneath the gravel and you have to install the filter plates before adding the gravel.
If you get an internal power filter it gets rinsed with freshwater, assembled and then put in the tank after the gravel has been added.
If you get a hang on back (HOB) style filter, these go on after the tank has been filled with water.
If you get an external canister filter, these also get rinsed with freshwater and then assembled and connected to the tank by a couple of plastic hoses. These get set up after the tank has water in.
Once the filter is set up, top the tank up so it is reasonably full and turn the filters on. Allow the tank to run for at least a few days before adding any fish. You can either do a fish in cycle or a fishless cycle. A fish in cycle means you have a few fish in the tank while the filters develop beneficial bacteria that keep the water clean. After a month or so you can usually add a few more fish.
A fishless cycle means you have no fish in the tank while the filters develop the beneficial filter bacteria and you have to wait for a month or so before adding any fish.
There is more info on cycling filters at the following link
http://www.fishforums.net/threads/cycling-your-new-fresh-water-tank-read-this-first.421488/
------------------------
As to whether or not you should get cichlids, there are lots of cichlids available and most do very well in aquariums. They range in size from 2 inches to 2 feet and come from soft acid water to hard alkaline water, so there are lots to choose from. However, we need to know what the general hardness and carbonate hardness of your water supply is before we offer ideas. Also tank size needs to be taken into consideration because most cichlids are territorial.
