A 60 liter tank is an excellent starter size & most fish shops will do a coldwater kit - suitable for goldfish including a tank with a lighted hood & an internal filter plus a starter size of water conditioners & food. This will cost around �70 - 80. You will also need to add sand or gravel for the bottom & some plastic or real plants & maybe a decoration. You will need a length of pipe & or a gravel cleaner to syphon out the dirty water from the bottom, small bottle brush to help clean the filter, replacement filter media, a net to catch your fish when necessary. You will need to set up the tank ahead of time because you need to get the filter started. All explained in the tank instructions.
Then you get to choose your fish. Have a look on the net at all the different varieties of fancy goldfish available. A regular pond fish will be cheap but it will soon outgrow your tank. Fancy fish are slower growers & will live for about 10 - 14 years.
If you want tropical fish your set up will cost a little more because a water heater will be included. You will be able to have more smaller fish in a tropical set up than goldfish in the same size tank. Beginner tropical fish for 60 litres are;
6 x Corydorus,- eat up any food scraps from the others & sit on the bottom.
1 boy + 3 girl mollies, silver, black & orange livebearers - have live baby fish instead of laying eggs.
1 boy + 3 girl platies, yellow, red, orange & black livebearers.
1 albino Ancistrus bristle nose catfish to eat all the algae from the tank & must have a piece of bogwood to live on.
The total set up will probably cost around �100 - 120.